History Main / SuperpoweredEvilSide

* Dark Cupid gets more than he bargained for in ''Fanfic/{{Spellbound}}'' when he hits Chat Noir with one of his MindControl arrows. Since Adrien is half-fae, and his fae side is resistant to magic, the arrow merely suppresses his human side -- the side that has recognisable morality and compassion and other such niceties like restraint. He proceeds to enjoy beating Dark Cupid to a pulp, and would have outright killed him if Ladybug hadn't intervened.

** The depth of this is such that Willow, the cutest, sweetest, and most innocent of the Scoobies at series start, becomes the only non-Giles member of the Scoobies to have directly murdered an innocent person. (Glory wasn't innocent, but the human Ben was)

* In ''Webcomic/RiseOfTheHeroes'' Andrew LaCondore slips into a twisted version of himself after submerging and drowning at sea. It is referred to as an 'Overlord' form by Cate. Needless to say, it comes with a crazy amount of strength and the ability to manipulate dark flames.

** Once magic trade-offs are explained to Elliot, [[https://www.egscomics.com/comic/balance-090 he]] [[https://www.egscomics.com/comic/balance-091 points]] [[https://www.egscomics.com/comic/balance-103 out]] he could trade an EvilCostumeSwitch for more power. Which he [[https://www.egscomics.com/comic/balance-131 eventually does]].

** Once magic trade-offs are explained to Elliot, he point out he could trade an EvilCostumeSwitch for more power. Which he [[https://www.egscomics.com/comic/balance-131 eventually does]].

* While "Fallen Grace" (a.k.a. "Dark Omega Grace") from ''Webcomic/ElGoonishShive'' falls much closer to the CrouchingMoronHiddenBadass type, she still deserves mention here. Not only is Fallen Grace actually willing to use her shape-shifting powers as a weapon -- unlike the pacifistic (NOT TechnicalPacifist) Grace -- she's also got access to the Lespuko Spurs; special claws that retard healing, thus neutralizing the advantage of the HealingFactor. She's also got horns, HellishPupils, and [[SpikesOfVillainy a whole lotta spikes]].

%%* Shandala in ''WebAnimation/BrokenSaints'' has [[BreakTheCutie some]] [[BewareTheNiceOnes serious]] [[NightmareFuel issues]].

* Shandala in ''WebAnimation/BrokenSaints'' has [[BreakTheCutie some]] [[BewareTheNiceOnes serious]] [[NightmareFuel issues]].

* Niki in ''Series/{{Heroes}}'' has her amoral alter ego Jessica ("[[FanNickname ikiN]]"), who has sole control of her super strength [[spoiler:until the finale, when Niki finally gets to use it for herself. She might have used it once on impulse a few episodes prior to stop an attacking policeman -- this is debatable.]] In the second season, it was explained that [[spoiler: some people suffer a dissociative break to cope with the new reality of being a metahuman. When Niki conquered the Jessica persona at the conclusion of the first season finale, she manifested a third personality named Gina several weeks later.]]

* ''WesternAnimation/MiraculousLadybug'''s third season features an episode called "Cat Blanc" ("Chat Blanc" in the original French), which depicts a BadFuture in which Cat Noir is Akumatized into the titular villain. He somewhat subverts the trope by being insane and desperate to fix the damage he created by accident, desperate to the point of being willing to kill Ladybug and destroy the universe and PutThemAllOutOfMyMisery, but fits the "Superpowered" side of the trope to a T. Cat Noir's destructive powers are formidable to begin with (he once destroyed an entire PocketDimension in a previous episode), but his first act as Cat Blanc is a blast of destructive energy that cut the moon in half and decimated all of Paris with the recoil alone. This includes the villain Hawk Moth, who probably [[DidNotThinkThisThrough didn't consider the ramifications of deliberately traumatizing his own son and then giving him "unlimited powers of destruction"]].

* ''WesternAnimation/TeenTitans'':

* ''Literature/VillainsByNecessity'': [[spoiler:Sam]], courtesy of Valeriana's medallion.

* SuperpoweredEvilSide/WesternAnimation

[[folder:Myths & Religion]]

[[folder:Pro Wrestling]]

!!Example Subpages:

!!Other Examples:

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[[quoteright:350:[[ComicBook/{{Etrigan}} https://static.tvtropes.org/pmwiki/pub/images/139c1592b0b684a92c74e6c32d5ede2a.jpg]]]]
[[caption-width-right:350:"Jason Blood, born of man\\
A hidden evil lies within\\
Spoken verse awakens sin\\
And frees the demon Etrigan"]]

%% Caption selected per above IP thread. Please do not replace or remove without discussion here:
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* In ''Fanfic/ChildOfTheStorm'', Harry has a dark side that starts appearing after chapter 50. While not strictly another personality, it's certainly another side of him. According to Carol (who's had a look inside his mind), like all the experiences that should have screwed him up have been locked away in a box in his mind, constituting his dark side. It's [[TranquilFury frighteningly cold]], ruthlessly calculating, and while not explicitly more powerful, Carol describes it as TheUnfettered, while others describe it as being frighteningly reminiscent of a young Magneto. In one early appearance, it resulted in Harry putting an entire HYDRA assault team at his mercy and nearly forcing a PsychicAssistedSuicide after their leader took a child hostage, only being talked down by Jane. Then, a chapter later, it led to him telekinetically ripping Gravemoss' ribcage open and tearing his heart out (not that it had [[HealingFactor any long term effect]]). Unsurprisingly, [[BestFriend Carol]] [[MoralityChain keeps a close watch on him]], as Harry does on himself, being invariably horrified by what he's done when it sinks in.
** Towards the end of the first book, Harry's protection is revealed as a fragment of the Phoenix Force, and the start of ''Ghosts of the Past'' shows that he can tap into it. Considering the already mentioned dark side and that the Phoenix has taken him over to protect him, appearing in the gear of the Dark Phoenix and destroying everything in its way, this is rather worrying - while the Phoenix is broadly benevolent or at least, [[spoiler: Lily, the White Phoenix of the Crown,]] is, the power itself is a) morally neutral, b) incredibly volatile. As a result, Loki's fear is that that the two will combine and turn him into the Dark Phoenix. [[spoiler: This fear turns out to be entirely justified.]]

* Dark Cupid gets more than he bargained for in ''Fanfic/{{Spellbound}}'' when he hits Chat Noir with one of his MindControl arrows. Since Adrien is half-fae, and his fae side is resistant to magic, the arrow merely suppresses his human side - the side that has recognisable morality and compassion and other such niceties like restraint. He proceeds to enjoy beating Dark Cupid to a pulp, and would have outright killed him if Ladybug hadn't intervened.

* [[spoiler:Beranabus]], in Darren Shan's [[Literature/TheDemonata Demonata]] series. [[spoiler:As a result of being half demon, he was able to turn into one. He does this only once, because he's afraid that this ability is one of these, in order to fight [[CosmicHorror Death]]. He succeeds in his goal of sending it back into the demonata's universe, but dies in the process.]].

** Greg Hartmann is an amoral, egoistic and hypocritical politician who doesn't care about whom he uses, kills, maims, or hurts in his hunt for power. He is clearly an evil character, but he is absolutely lovely compared to his alter ego Puppetman, a complete sadist and sociopath who uses his potent emotion manipulation power to bring out the worst in everyone and only lives to revel in the violence and horror he creates.

** ''Series/TheFlash2014'': In the third season, Caitlin starts manifesting her Earth-2 counterpart's superpowers. Eventually, this starts to result in the Killer Frost persona taking over, complete with white hair, icy blue eyes, and a reverbing voice, not to mention the cold powers. It's made clear that Caitlin and Frost are constantly struggling for control. This is foreshadowed by Frankie Kane, whose body is occasionally taken over by her Flashpoint counterpart Magenta, with glowing magenta eyes, an evil smile, and metal control powers. Barry is able to talk Frankie into reining Magenta in, though. (As for Caitlin, after a several-episode run in full Killer Frost mode, when Savitar is on the verge of finishing Cisco off, she finds she can't bring herself to allow it, and returns to Team Flash for the final battle - but ''not'' to her original pre-powers personality. Even she isn't sure who she is anymore, and pulls a TenMinuteRetirement while she rediscovers herself between seasons.) Frost eventually develops into more of a JerkWithAHeartOfGold, acting as a SuperpoweredAlterEgo to Caitlin.

** The emphasis here is on the superpowered - Dark Willow is arguably the most powerful known being in the Buffyverse.
** As time goes on, Willow seems to have her Super-Powered Evil Side under control. It's more that she turns evil when she uses powerful magic, but then she turns back good when she stops. A scene in Season Seven demonstrates this effectively: while using a powerful barrier spell to protect an innocent girl from a spider demon, Willow gets the black eyes and black hair, and also calls the girl a bitch. After the demon leaves, she goes back to normal, and apologizes to the girl.

* Niki in ''Series/{{Heroes}}'' has her amoral alter ego Jessica ("[[FanNickname ikiN]]"), who has sole control of her super strength [[spoiler:until the finale, when Niki finally gets to use it for herself. She might have used it once on impulse a few episodes prior to stop an attacking policeman--this is debatable.]] In the second season, it was explained that [[spoiler: some people suffer a dissociative break to cope with the new reality of being a metahuman. When Niki conquered the Jessica persona at the conclusion of the first season finale, she manifested a third personality named Gina several weeks later.]]

** [[spoiler:Isobel the witch]] becomes this for Lana in season four.

** Gordon Godfrey has [[spoiler:{{ComicBook/Darkseid}}]] in season 10.

** And Dean Winchester, in a way. In season 10, [[spoiler:The Mark Of Cain turns its bearer into a heartless evil murderer who loves brutally killing everyone, and has the potential to turn them into a demon]], and demons tend to have super-strength. In the past, Dean would punch an angel and doing it is like punching an iron wall; Painful. In Season 10, [[spoiler:the Mark turned Dean into a demon, he was cured and turned back into his human-self, but the Mark still affected him and slowly turned him into this cold-blooded killer. It also enhanced his raw physical strength because he managed to beat the crap out Castiel; an angel he already punched before, but it didn't even left a mark and he nearly broke his hand hitting him. Yet Dean was able to beat the same angel into a bloody mess and leave him laying on the floor with probably a broken nose. Now, granted Castiel wasn't at full strength at the time, but Dean also punched Cupid once and almost broke his fist, and surely Castiel would still remain stronger than a low-ranking Cupid, even when he's half-de-powered... right?]]

* Myth/EgyptianMythology: In the ''Book of the Heavenly Cow'', Ra sent Hathor - the matriachal bovine goddess - to punish a group of mortals who had conspired against him. Hathor transformed into the leonine war-goddess Sekhmet and decided to just [[OmnicidalManiac kill everything]] instead, and was only stopped and turned back into Hathor when Ra tricked her into getting drunk on beer dyed to look like blood.

** ''TabletopGame/WraithTheOblivion'': Wraiths have got their Shadow, a second personality usually existing within the wraith trying to make them them give up their struggles and descend into nonexistence or permanently hand over control of their body. Depending on the Shadow, this might take many forms, some direct and some seemingly helping the wraith. The latter type often has ways to enhance the wraith's body when temporarily in control - better attributes, more magic powers or even items appearing only during the Shadow's catharsis. Such wraiths then always have the ability to let their Shadows handle combats too tough for them, but are generally loathe to do so because there's no telling what else the Shadow might do while in control.

* ''Machinima/RedVsBlue'': A fairly goofy example occurs in episode 40: in order to fight off a horde of "noobs" in Battle Creek, Caboose gets in touch with his "angry side", which results in him gunning down the noobs while shouting bizarre threats like "I will eat your unhappiness!" and "Your toast has been burned, and no amount of scraping will remove the black parts!"

* In ''Webcomic/AliceAndTheNightmare'', Alice is implied to have something like this - whenever she gets angry, her eyes start to glow and she spills red dust (sign of dream magic) around. It seems that the medicine she takes daily keeps it at bay.

* In ''Webcomic/{{Gnoph}}'', Will's symbiotic partner Lyss usually acts as a [[BondCreatures Bond Creature]]; but when he passes out and she takes full control of his body, she acts like an example of this trope, due to being AxCrazy and having no compunction against killing (or ''[[ImAHumanitarian eating]]'') humans.

* While "Fallen Grace" (a.k.a. "Dark Omega Grace") from ''Webcomic/ElGoonishShive'' falls much closer to the CrouchingMoronHiddenBadass type, she still deserves mention here. Not only is Fallen Grace actually willing to use her shape-shifting powers as a weapon -- unlike the pacifistic (NOT TechnicalPacifist) Grace -- she's also got access to the Lespuko Spurs; special claws that retard healing, thus neutralizing the advantage of the HealingFactor. She's also got horns, HellishPupils, and [[SpikesOfVillainy a whole lotta spikes]].

* ''Webcomic/SweetHome'': Each infected person develops one of these. They serve as a means of determining exactly how those that were infected will end up mutating. Hyun's in particular is very eager to play mind games with him.

* In the "Angry Video Game Fag" by [[Website/TheDeadHorseInterchange Ebeeto]], Ebeeto "transforms" into The Angry Video Game Fag whenever he is angered enough. The transformation comes complete with a video-game-inspired cutscene.

* A flashback in episode 19 of ''WesternAnimation/GeneratorRex'' reveals that Rex can turn into a savage biomechanical GiantRobot Evo. One of the reasons White Knight is so hard on Rex is that he is afraid of Rex becoming that monster again. Rex himself has no clue he can do this thanks to his amnesia.

* In ''WesternAnimation/KipoAndTheAgeOfWonderbeasts'', Kipo discovers that in moments of stress she grows fur and gains superhuman physical abilities. In season two, it's revealed that this is because she has the ability to turn into a [[MegaNeko Mega Jaguar]]. However, if she actually transforms, she risks losing her mind to the jaguar's instincts [[spoiler: like what happened when her mom turned into the Mega Monkey]].

* ''WesternAnimation/TheOwlHouse'' ends up subverting this--[[spoiler: Eda suffers from a curse that causes her to transform into a violent rampaging monster called the Owl Beast, which Eda and everyone else assumes is this. But it's revealed in Season 2 that the Owl Beast is actually a separate creature [[SealedinAPersonShapedCan imprisoned in Eda's body]] and it ultimately wants to be free from the curse just as much as Eda does. Learning this allows Eda to form a truce with the Beast, giving her access to its powers (provided that she asks politely and eats some voles for it).]]

** A splashing of chemicals prompts good-natured vegetarian Beast Boy to turn into a surly, meat-chomping bad boy who later turns into an anthropomorphic wolfman that was capable of taking on the entire team (as well as another wolfman). Later it's explained that, instead of turning Beast Boy into an actual lycanthrope, the chemicals only unleashed what was already there (which makes no sense considering that [[spoiler: they also changed Adonis]]), and he's given an antidote so that he won't transform against his will. He once again manifests this hidden wild side in a battle against Slade, slicing through a number of his goons before Slade puts a stop to it with his own supercharged powers. Possible subversion: It's made quite clear that "Man-Beast" isn't evil, just a really powerful, rather intelligent animal. Like any animal, it becomes hostile when scared, but generally it keeps to its human form's wishes. Beast Boy still expresses concern that it's still inside him at the end of the episode. He does seem to have acquired a degree of control over it later on, though he rarely uses it. In its first appearance, though, the Beast is more like [[ComicBook/TheIncredibleHulk the Hulk]]--not evil, but uncontrollable, volatile, and dangerous.

* In ''WesternAnimation/WinxClub'', Lord Darkar uses his dark magic to turn Bloom into her Superpowered Evil Side in the form of Dark Bloom, who is Bloom with a black version of her fairy outfit and demonic yellow eyes. And he does it twice with her in the second season. Once to have her ship off Alfea's Codex piece to him through his TeamPet Kerbog, and again to have her help him open the portal to Realix with the four Codex pieces where he can acquire the Ultimate Power. Both times had her turned back to normal in the end - for the first time, the impostor Professor Avalon used his wand to lift the spell, and for the second time, it was Prince Sky who changed her back through his words of kindness, especially his "I love you" line, after which she returns the Ultimate Power to its rightful place to Darkar's shock and dismay.

* Many characters in the Franchise/{{Nasuverse}} have an "inversion impulse", the desire to go psycho and unleash the full power their bitchin' superpowers on the world in an orgy of murder, due to their monstorous bloodlines.

** One particular exception to this "evil doppelganger made by the BigBad" is Archetype Earth: She is a fragment of Arcueid subconscious, and if she wakes up and takes over her host, she can show how utterly powerful Arcueid could have been compared to her usual self, such as casually trying to destroy the world on a whim.

!!Examples:

[[folder:Anime & Manga]]
* Urd of ''Manga/AhMyGoddess'' (at least in the anime). She has a divine father, a demon mother, and the demon half is ''scary'' when it gets loose. She nearly destroys a Power Absorber, which can one-hit knockout some fairly powerful angels, goddesses, and demons.
* In ''Manga/AirGear'' one of the strongest members of the protagonist's [[FiveManBand team]] has a split personality. Although Agito isn't exactly evil, [[AntiHero his aggressive, bloodthirsty behaviour]] and great skill at the series' [[SeriousBusiness title sport]] make him this to Akito, one of the gentlest characters in the series. Additionally, [[spoiler:later on Agito/Akito discovers he has a third personality named Lind who embodies this trope. He's the polar opposite of Akito and is implied to be much better at Air Gear than Agito. Although his intentions are still largely unknown, Agito himself warns the protagonist that Lind will probably end up becoming the main personality and betray him.]]
* In ''Literature/{{Anpanman}}'', Rollpanna is already a superheroine, but with two hearts: a good one and an evil one. Being under the influence of Baikinman or being near Anpanman triggers her evil heart, which powers her up even more, but she can break out of it when by her younger siblings, Melonpanna and Creampanda. Sometimes, Baikinman uses dirty tricks to completely remove her good side, turning her into Black Rollpanna, a ruthless fighter that is even more powerful than when she has both hearts, and nothing stops her, not even her siblings, until both hearts are together. For these reasons, she prefers to wander the earth alone, in fear of her evil heart being triggered.
* Eren from ''Manga/AttackOnTitan'' can become a Titan whenever he bites his hand. However, since the power of a Titan isn't easy to control (most of them are mindless ravaging beasts, after all), this tends to make him more ChaoticNeutral than ChaoticEvil like the regular Titans who eat people ForTheEvulz.
* ''Anime/{{Bakugan}}'': [[spoiler:[[TheHeavy Masquarade]] [[JekyllAndHyde is revealed to actually be]] ''Alice,'' the FriendToAllLivingThings and NiceGirl of the main team. A JekyllAndHyde complex was created do to being around her [[MadScientist grandfather]]'s laboratory at the time of an experiment that released powerful negative energy into the area. Masquarade is a cruel, sadistic, and incredibly powerful and strategic Brawler that plagues the main cast constantly; Alice is a [[NonActionGuy Non-Action Girl]] that acts as a {{Pacifist}}, wishing to avoid fighting altogether. This is also a case of GenderBender. There ultimately is a SplitPersonalityMerge, with Masquarade occasionally [[SpiritAdvisor appearing as a vision to help advise Alice in battling,]] and Alice going on to become an ActionGirl (who still keeps her NiceGirl personality).]]
* Dark Schneider/Lucien in ''Manga/{{Bastard}}''. Tiny, fifteen year old boy turns into the infamous eponymous bastard, the all-powerful Exploding Wizard. Then subverted since Darsh does a lot of dorky things outside of battle and seems much more like a JerkWithAHeartOfGold than anything else, with some people often remarking that compared to the Dark Schneider of fifteen years ago, this one is practically a ''saint''.
* Defied in ''Manga/BlackClover''. Asta is caught in dire straits the demon within his anti-magic sword attempts to tempt him into letting it take over with its power. Asta promptly tells it to suck it and punches the demon out to claim the power as his own, entering a demonic form called Black Asta. That said, when overcome by malice in his Black Asta form he's covered in more Anti-Magic and his powers are strengthened, playing this straight.
* ''Anime/BlackRockShooter'' (who is already not the nicest person out there), [[spoiler: after killing Dead Master the instant Mato enters her body]], becomes Insane Black Rock Shooter. IBRS is a lot more powerful and has better gear, but seems to hold Mato's happiness above literally '''everything else'''. And yes, that means she's willing to destroy the entire Other World, subjecting everyone else to the full effects of irreparable psychological trauma. Not to mention she '''never holds back''', even when faced against [[spoiler:Mato herself in a Black Rock Shooter avatar. And sure, you could say, "well Mato wanted to be hurt instead of BRS", and you'd be right, but that doesn't excuse IBRS from the downright crippling injuries she gives her with full knowledge that Mato '''cannot''' eat up as much pain as an Other Self.]] Long story short, when BRS is insane, you do '''not''' want to mess with her.
* Guts, the protagonist of ''Manga/{{Berserk}}'', is known to slip into this state during particularly tense moments. [[spoiler:In the manga, this becomes personified by The Beast, a feral lupine creature formed from the considerable amount of rage at the Godhand (and Griffith in particular) and other negative emotions that Guts suffers from after the Eclipse. When Guts is under The Beast's influence, he becomes a danger to everyone around him, even the people he loves -- at one point in the manga, [[NearRapeExperience he almost rapes Casca while under its influence.]] Later on, he acquires the Berserker Armor, an extremely dangerous cursed Dwarven artifact that blinds its user to pain and limitations and causes them to see everything as a threat. It also becomes a kind of physical conduit for The Beast.]]
* ''LightNovel/BeyondTheBoundary'': Akihito loses control of his [[HalfHumanHybrid youmu side]] after sustaining severe injuries. He is [[PersonOfMassDestruction immensely powerful]] in this state, requiring 3 people just to contain him. One stray fireball creates an enormous explosion when it hits a nearby mountain and he levels his surrounding area.
* ''Manga/{{Bleach}}'': Ichigo's inner Hollow is initially an extremely powerful, violent and monochromatic version of Ichigo. He ends up training Ichigo in how better to harness his Hollow and Shinigami power, but Ichigo has to beat him into submission to do it, or risk becoming a monstrous battle-frenzied BloodKnight as the price of power. Eventually, he learns how to harmonize with his inner power and can achieve his full potential without any loss of sanity and humanity.
** Which didn't help against Ulquiorra, which released the Evil Side after ''quite'' a massive [[TookALevelinBadass upgrade]], as he [[CurbStompBattle completely crushes]] Ulquiorra. This is actually a ''second'' Superpowered Evil Side. While Ichigo's inner Hollow is frenzied and vicious, it's capable of coherent speech and (often quite unorthodox) tactics. The new form he assumes against Ulquiorra is a single-minded, brutish but immensely powerful [[TheBerserker Berserker]] who mindlessly attacks everything in his path other than the person Ichigo had been focused on protecting at the time he transformed...even his other friends aren't safe from it.
* In ''Manga/Brave10'', it turns out [[spoiler:the sweet naive {{miko}} Isanami]] is the vessel for the DestroyerDeity [[spoiler:Izanami]].
* In the series ''LightNovel/ACertainMagicalIndex'', the main character Touma is shown to [[spoiler:have an actual sentient being inside of him that appeared after having his arm cut off. The guy who cut off said arm had an OhCrap moment when he realised that his power paled in comparison even though he reached the point of being higher than God. Note that Touma's name can alternately be read as "Invisible Demon Above God".]]
* ''Manga/Change123'' demonstrates why, in the real world, this is less of a cool new power and more of a deadly serious problem; you don't want your high-school girlfriend to snap and try to kill someone on your behalf because they said nasty things about you...[[spoiler:or to try to kill you because you tried to stop her from killing that person.]]
* Played with in ''Manga/{{Chobits}}''. Robot Persocom Chi has a personality living inside her called Freya. Freya always wears darker clothes, sports far less innocent expressions than Chi and is the one to take action to defend Chi when others threaten her. She's not evil, just less innocent than Chi and the holder of the answers to many mysteries of the series.
* The eponymous warriors of ''Manga/{{Claymore}}'' constantly run the risk of becoming "Awakened Ones" when using their powers. In that state, they become their Super-Powered Evil Sides without any chance of turning back to their original forms. The twist is [[spoiler:HeroicWillpower lets the sufficiently motivated come back from the brink and retain some control after completely transforming]].
* Wretched Egg is this to [[spoiler:Shiro]] in ''Manga/DeadmanWonderland''. [[spoiler:Shiro]] is a nice teenager while [[TheDreaded Wretched Egg]] is super-powered and incredibly murderous. [[spoiler:Subverted near the end when Shiro reveals that both personas were a lie. She's in control either way and is really a DeathSeeker.]]
* In ''Manga/DeliciousInDungeon'', [[spoiler: Falin was a powerful [[WhiteMagicianGirl mage]] anyway, but her [[BrainwashedAndCrazy Lunatic Magician controlled chimera form]] is on another level altogether. Makes sense as she now has the strength of the Red Dragon added to her own.]]
* Akira Fudou and Amon from ''Manga/{{Devilman}}'' may be the oldest example in the history of manga. And also an UnbuiltTrope, as the manga shows that having one wouldn't just conveniently let you send it out on enemy too strong for you to take - taking Amon's powers changes Akira from meek and gentle boy into complete BloodKnight and that even without letting Amon out. Amon however only breaks free in a SpinOff manga ''AMON'', and an OVA of the same title. In the anime Amon '''[[spoiler: eats a little girl alive]]''' and in the manga he is maybe just a bitter AntiHero, but still destroys several ''countries'', just by [[WalkingWasteland passing through them]].
* ''Franchise/{{Digimon}}'' has a few examples of this:
** In ''[[Anime/DigimonAdventure Adventure]]'', Taichi tries to force Agumon to evolve to perfect, causing the creation of [=SkullGreymon=].
** ''Anime/DigimonTamers'' has Megidramon formed when Takato watches Leomon die, who is so powerful the Digital World starts ''collapsing''.
** ''Anime/DigimonFrontier'' [[spoiler: Koichi]] spends about half the series as his SuperPoweredEvilSide Duskmon/Velgemon before it's revealed that he's [[spoiler: Koji's brother]] and gets his Digispirits purified to Loweemon/[=JagerLoweemon=]. He never seems quite as powerful after returning from the TheDarkSide.
** In ''Anime/DigimonDataSquad'', Marcus' emotion get the better of him, too, forcing [=ShineGreymon=] to enter ruin mode.
** ''Anime/DigimonFusion'' has two examples--[=DarkVolumon=] for [[spoiler: Ballistamon]] and the Whisper virus for [[spoiler: Apollomon]]. Surprisingly enough, Shoutmon averted this by having no "evil" powered side.
** ''Anime/DigimonAdventure2020'' has this happen to Agumon again, [[spoiler:but for his Mega evolution when his partner gets too furious in his desperation to protect his friends from [=DoneDevimon=], Digivolving him to ''Machinedramon'']].
* Son Goku of ''Manga/DragonBall'' faced this early on with his Oozaru transformations. In this form he loses all sense of self while gaining immense strength and size; the best solutions found were to either cut off his tail or ''blow up the moon''. The transformation into the Oozaru, while generally a bad thing, did have two positive outcomes. One was the escape of Goku and friends from Emperor Pilaf; the second was Gohan defeating Vegeta... by landing on him.
** ''Anime/DragonBallGT'' takes Oozarus UpToEleven when Goku transforms into one as a Super Saiyan. Think a giant raging ape is bad? Try a giant raging Super Saiyan ape. Though Goku's able to come to his senses, which sparks his transformation into a Super Saiyan 4.
** The Super Saiyan state acts like this without proper training. The transformation occurs in a moment of pure rage, and the resulting personality shift leaves the Saiyan struggling with an overwhelming anger. In the Cell Saga, Goku and Gohan train in order to resolve this issue, making Super Saiyan as natural and comfortable as possible so they can maintain it without extra effort as well as retaining their own personalities.
** Frieza even comments on this when Goku beats him around as a Super Saiyan. He asks if Goku isn't being as cold blooded as he is, and concludes that Goku is still struggling to control the rage in him and that it's uncertain if he will win.
** Son Gohan's Super Saiyan 2 form is a truly chilling example. It is more than a little disquieting to watch the kindhearted and sensitive little boy we have come to care about over three sagas turn into a gleefully cold-blooded sadist when he achieves the Messianic power of Super Saiyan 2.
** In the Buu Saga, Vegeta falls under Babidi's mind control, becoming Majin Vegeta. However, it turns out that Vegeta is NotBrainwashed: he ''let'' Babidi put him under the wizard's "control" for the power boost that comes with it, and is perfectly capable of ignoring Babidi's commands (because they distract Vegeta from the reason he did it in the first place: fighting Goku).
** In ''Anime/DragonBallSuper'', we have Kale, a Saiyan from Universe 6. Her "Super Saiyan Beserk" form is just as violent as Broly's Legendary Super Saiyan form. Cabba could barely survive and Caulifla had to bail him out.
** Surprisingly, ''[[Anime/DragonBallSuperBroly Broly]]'' is a downplayed version of this, as when he turns Super Saiyan and loses all his sanity, he is more like a feral beast than a raging psychopath, even fighting with himself to avoid killing somebody.
* In ''Manga/DGrayMan'', Allen's [[EmpathicWeapon Innocence]] seems to have a mind of its own and tends to upgrade itself when Allen gets particularly angry or emotional. It also can control Allen when he's unconscious, and it tends to be very vicious. Then again, it's only dangerous to [[TheHeartless Akuma]].
** Also Arystar Krory, although he has less of a Super-Powered Evil Side than a Super-Powered DeadpanSnarker badass Side.
** There's also the Noah, although they're [[AffablyEvil (affably) evil]] to begin with.
** Allen, with the Fourteenth Noah [[spoiler: who is now making himself heard in conversation, if only to mess with ''the Millennium Earl's'' head.]] The Fourteenth hasn't been seen in actual combat yet, so "superpowered" may still be in question (yeah, right), but [[spoiler:his brief awakening in Allen is enough to terrify a Level 4 akuma and his ability to make Allen display a truly nasty SlasherSmile]] definitely hints at the evil part.
*** In the most recent chapters, [[spoiler:after Kanda stabs Allen and awakens his Noah side,]] there are clear hints that the Fourteenth is ''terrifyingly'' powerful, even by Noah standards. Remember, [[spoiler: this is the guy who apparently ''by himself'' managed to kill off nearly all the previous incarnations of the Noahs and severely injure the Millennium Earl several decades ago]], to wit his laughter after having ''just woken up'' is mistaken for a minor earthquake.
* ''Manga/DNAngel'':
** Satoshi has [[spoiler: Krad, one half of an extremely powerful artwork who likes killing people,]] living in his head.
** Daisuke has Dark, [[spoiler: the other half of the same artwork]], living in HIS head, although Dark's more mischievous than evil.
** Krad's fandom nickname: Homicidal Blonde.
* Lucy from ''Manga/ElfenLied'' is a variant of this trope - while she was originally the 'true' personality, she suffered a nasty head wound that caused SplitPersonality and left her [[HelplessGoodSide nonpowered good side]], CuteMute Nyuu, in control. The times when her 'true' self resurfaces fit this trope to a tee.
** In the manga, we learn that [[spoiler:Lucy - or rather, [[OnlyKnownByTheirNickname Kaede]] - is actually more of a superpowered ''neutral'' side, who's been listening to and partly controlled by a completely insane OmnicidalManiac ''third'' personality (created by either her Diclonius instincts or by [[BewareTheNiceOnes snapping]] as a result of [[KidsAreCruel the]] [[OrphanageOfFear torment]] [[BreakTheCutie inflicted]] [[AllOfTheOtherReindeer on]] [[MuggingTheMonster her]] when she was young, whichever theory you prefer) that wishes to annihilate the entire human species, if not all sentient life.]]
* [[spoiler:Vincent Law's proxy form]] is initially presented as this in ''Anime/ErgoProxy''. [[spoiler: As the series progresses, it is later revealed that "Vincent Law" is just the alias for the Proxy of Death: Ergo Proxy]]
* [[EvilGenius Brain]] from ''Manga/FairyTail'' has [[AxCrazy Zero]], who is twice as strong as him and far more adept in combat, being credited as the ''true'' master of Oracion Seis. He's so dangerous that Brain sealed him away [[spoiler:with special keys that link all the members of the Oracion Seis, and he emerges when the Oracion Seis are all defeated to finish what they started.]]
** Also Rogue, whose magic causes the darkness in his heart to manifest as his shadow, tempting him to do evil and even possessing him once to give him a power up and try to force him to kill.
** [[spoiler: Natsu, as it turns out, is the true identity of E.N.D., the most powerful demon ever created by the BigBad, Zeref. While not much else is known about him, its indicated that even the dragon Acnologia is leery of him, which no doubts says a lot about E.N.D.'s power level.]]
* Quiet and retiring Haru's alter ego, "Black Haru," from ''Manga/FruitsBasket'' is a humorous take on the trope. In the anime (or early in the manga), at least. It's played for some serious drama later in the manga. Along the same vein, that goes for the brief 'cameo' of [[spoiler:"Black Yuki"]] in the later chapters as well.
* Ginji's Raitei persona in ''Manga/GetBackers''. [[spoiler:Kazuki]] also has one, when [[spoiler:he releases the seal on his Stigma eye.]] The same way Ginji is the "Thunder Emperor," he's "the Prince of Terror."
* Kagura, the adorable, profane, sukonbu-chewing, nose-picking heroine from ''{{Manga/Gintama}}'' [[https://youtu.be/Xq0TPJXW8vo can go into this]] when the self-imposed chains on her Yato blood get broken. She stops fighting to win and instead fights to kill with a savagery that scares her.
* ''Manga/GreenWorldz'': Akira, the survivor most of the story has focused on so far, has a darker personality hidden within him that tends to come out when he's at a crossroads and pushes him to survive and adapt to their post-apocalyptic world, even if doing so sometimes requires him to do unethical things.
* This happened in ''Manga/{{Guyver}}'' once, but it was a doozy. [[spoiler:After his father was turned into an Enzyme Zoanoid and ripped out Sho's brain, the Guyver itself took over Sho and killed his father. Let's just say that when he found out, he didn't take it well.]] Though this wasn't so much the Guyver being evil, as obeying its Prime Directive of wearer-preservation.
* In ''Manga/{{Hellsing}}'', Seras Victoria's berserker mode could be counted as her Super-Powered Evil Side.
* In ''Anime/HeroicAge'', the giant mech-like warriors of the Heroic Tribe, called the Nodos, can eventually let out a Super-Powered Evil Side when two fight together - whether against each other, or side by side - called Mental Chaos, when they enter a pure blind berserker rage. Considering a single Nodos can sometimes destroy a whole planet on its own at its normal levels of power, a Nodos in Mental Chaos is a frightening thing indeed. In Bellcross, the Nodos that serves the human Age, Mental Chaos is shown by his skin and "armor" turning dark gray, almost black, and a set of blue spheres implanted in his body begins to glow bright red. And he roars a lot. Then he begins ''leveling whatever galaxy he's in at that moment, before moving on to another area''.
* The main character of ''Manga/IkkiTousen'', Sonsaku Hakufu, is a token IdiotHero with enough fighting skill to beat the crap out of a school attended only by martial artists and assorted thugs. But sometimes the enemy is just above her [[PowerLevels level]] and she finds herself beaten almost to death: vision blurs, strengh fades... [[OhCrap Congratulations!]] You've awakened "the power of the dragon" and the last thing you are likely to see is her raptured expression, while she [[NightmareFuel strangles you to death]] or is about to stab you with a sword. To be honest, everyone possessed by a dragon soul behaves this way... even if [[BewareTheNiceOnes not a fighter]] -- the biggest example is Gentoku Ryuubi, a ButtMonkey CuteClumsyGirl who happens to possess a Dragon Soul ''even more powerful than Hakufu's'', and when taken over by it she becomes a totally savage PersonOfMassDestruction.
* The "berserker spirits" aka The Dragons from ''Manga/IkkiTousen''. So far, we have four dragon holders: Hakufu, Ryuubi, Sousou, and [[spoiler:Ryoumou]]
* ''Manga/InuYasha'':
** Inu-Yasha's demon side, although it could also be interpreted as WithGreatPowerComesGreatInsanity, as his bouts of insanity stem from having too much demonic power for his half-human body to handle. His EmpathicWeapon Tessaiga acts as a RestrainingBolt. Subverted in that eventually Tessaiga itself is so powerful that his demon side is actually [[PowerupLetdown weaker]] by comparison. (He was in fact given so powerful a weapon so he wouldn't need to rely on his own demon powers.)
** Suikotsu of the Band of Seven is a [[TheMedic doctor]] with SplitPersonality whose darker side is a sadistic, blood-thirsty murderer. It turns out that ''this'' is his true self, as well: he'd been good, gotten [[BloodKnight a taste for battle]] when defending his village, and became a mad killer of his own free will. The purifying effect of the mountain the story takes place on lets him revert to the decent man he'd once been.
* In the h-anime ''Makai Tenshi Jibril'' (Translated title: ''Jiburiru - The Devil Angel''), {{Meganekko}}-with-a-crush Meimi is given the sadistic MagicalGirl persona of Misty May, the "Devil" counterpart to the heroine Rika (St. Jibril/Jiburiru). Closer to the trope definition would be Rika's evil form in the sequel, or Hikari's Black Aries form in the third game.
* In ''Manga/JujutsuKaisen'', Itadori has Ryomen Sukuna, the strongest cursed being, as his super powered evil side. Itadori's journey is about getting and consuming all of Sukuna's fingers, so that he can hold all of Sukuna within him and be executed, destroying him once and for all.
* ''Franchise/KagerouProject'': Konoha, SuperPoweredAlterEgo for IllBoy Haruka Kokonose, is a downplayed example. While he is in fact a very caring individual - like the real Haruka - it is noted by other characters that despite noble intentions, [[SuperStrength he uses]] [[FlashStep his powers]] to solve problems with violence and destruction. [[spoiler:Not to mention that he's a DemonicPossession away from being used to massacre every other main character, [[GroundhogDayLoop and does so every few thousand years]]]].
* In ''VisualNovel/KamigamiNoAsobi'', [[spoiler: [[Myth/NorseMythology Baldr]], the God of Light]] has one, as the [[WalkingWasteland God of Destruction]]. [[spoiler: And Loki, who loves him, will have to kill him to prevent his evil side from destroying the world]].
* When Kazuma of ''LightNovel/KazeNoStigma'' taps into his evil side (really a reversion to his old behavior in his backstory), he will do whatever it takes to accomplish his goals, no matter who he has to hurt (or mind crush!). [[spoiler:Kazuma may actually be a subversion if Ayano is correct in her analysis when she faces him to try and stop him from going on his rampage. She states quite clearly that he used to be so overwhelming that it seemed to be stupid to be afraid of him. Because she was afraid, it was proof that he was weaker than before. In any case, he's still very kick ass. She's right. When he's in this state he's basically letting his anger and pride control him (something he had often warned others against), lacking the ability and focus that he'd shown in the rest of the series. This fight is also the first time that she gets the best of him, first [[WhatTheHellHero calling him out for his behavior]], then landing a solid hit that knocks him off his feet.]]
* When Yuuri from ''LightNovel/KyoKaraMaoh'' reaches an appropriate level of moral outrage, he involuntarily transforms into a larger version of himself with cooler hair, amazing magical powers and a thirst for justice.
** ...who almost always ''says'' he's going to kill people, even though he 'dislikes bloodshed', but has no confirmed kills, and is usually confirmed as not having hurt anyone. Once he sentenced an UnluckyChildhoodFriend and her quarry to go on a date. Another time he mistook an assassination attempt for an earthquake and saved everybody, even the enemy soldiers who'd been trying to kill him. Also, he has been known to say nonsensical things about fire brigades etc., just like Yuuri always does, just in a serious, booming way.
** In the manga he gets a lot closer to the 'evil' line, but is a lot less divorced, in terms of identity, from normal Yuuri, whose lifelong tendency to a really violent temper is underlined. But the manga is darker than the anime. And Yuuri accidentally stabbed Wolfram half to death a while back in the novels. Genre Woobiefication?
* Ryner Lute from ''Anime/TheLegendOfTheLegendaryHeroes'' is lazy but if you hurt one of his friends, you will see why Alpha Stigmas are feared: an evil God of Destruction personality with overwhelming powers will just disintegrate you.
-->'''Ryner Lute:''' First comes destruction. I bring forth nothing. I bless nothing. I save nothing. I just erase. Completely.
* In ''Anime/MagicalProjectS'' Misao is normally a shy, physically weak and powerless girl, but when she transforms into her evil side, Pixy Misa, she becomes super confident and super competent. At full power she is able to easily defeat the heroine Sasami.
* Tohma in ''Manga/MagicalRecordLyricalNanohaForce'' has his Black Knight form. When it comes out, he gains a HealingFactor, powerful magic, and is capable of performing a Zero Effect, which greatly drains the energies of anyone and anything in a wide area. Unfortunately, he loses over half his consciousness in this form, replacing it with an insatiable need to kill.
* Mayo Kagura from ''LightNovel/MaiHimeDestiny''. In a series where everyone has {{psychic powers}}, it's hard to stand out when you have boring ol' telekinesis... unless you have a Super-Powered Evil Side that can ''uproot trees and use them as weapons''.
* In ''Anime/MobileSuitGundamSEED'', Andrew Waltfeld seemed to likened SEED Mode to berserker rages of the Vikings. While it's not an actual Super-Powered Evil Side, activating SEED Mode while enraged is certainly a glorious mess.
* While not necessarily "evil," a mechanical version of this can be found within ''Anime/MobileSuitGundamWing'', specifically in the form of the Zero System, a computer system in the Wing Zero which interfaces with the pilot's brain, enhancing his reaction time and aggressiveness, and allowing him to process tactical data with superhuman speed and efficiency... with a fun little side effect of driving the pilot temporarily AxCrazy. Given that they're still inside a giant, city-killing death machine with all their piloting skills boosted, results are predictably messy.
** The Zero System ''can'' be used safely: the pilot must keep a clear head and not be conflicted in his thoughts towards the battle. In this case the pilot then gains all the benefits without the insanity. Both Heero and Zechs reach this point in the end - and, in fact, Heero eventually becomes so relaxed about the obligatory in-cockpit MindRape that he starts offering it to his fellow pilots as ''therapy''. Astonishingly, [[EpiphanyTherapy it works]].
** ''Anime/MobileSuitGundam00'' also has fun with this - Allelujah Haptism has a SplitPersonality: Hallelujah, a blood-thirsty "warrior" half who is more skilled than any other pilot in Celestial Being. Then subverted with [[spoiler:The "Ultimate Soldier", aka [[FanNickname H/Allelujah or Doublelujah]], who's an even ''better'' pilot and integrates the best parts of both personalities, including Allelujah's morals.]]
** In the ''[[Anime/Gundam00AWakeningOftheTrailblazer Gundam 00 movie]]'' his mech, the Harute, gets one of its own called Marute.
** From ''Anime/MobileSuitGundamUnicorn'', there's the Unicorn Gundam. Normally a high performance mobile suit with generally above average statistics but nothing of any particularly remarkable quality, when the pilot and it come into contact with a Newtype enemy and the pilot feels a strong enough emotional pull (usually anger), the Gundam feeds off of it and transforms into the eponymous Unicorn Gundam, now in its "NT-D" (Newtype Destroyer) Mode. Its speed ramps up significantly, its strength seems to increase, it gains new abilities related to its psycoframe, and worst of all the suit's AI will stop at nothing short of a manual override or a HeroicRROD to kill any Newtype in weapon range. This is entirely not good for anyone who happens to be facing the thing down, as it generally goes from on an even footing or slightly underperforming the enemy to stomping their face in on a [[CurbStompBattle one-sided epic beating.]] After falling victim to this once or twice, Banagher learns how to consciously activate the NT-D system and override its AI, leaving him in complete control of the suit.
* Mob's ???% form in ''Manga/MobPsycho100'' comes out when Mob falls unconscious, and is not only far more powerful than Mob at even 100%, but is also far less restrained in how it uses that power - though, as a defense mechanism, it doesn't seem actively malicious.
* Piss off the softspoken, easygoing and always smiling Wolfgang Grimmer, from Creator/NaokiUrasawa's ''Manga/{{Monster}}'', and you'll have to deal with "The Magnificent Steiner". [[NoHoldsBarredBeatdown Carnage ensues]] - though it's never directly shown. This is how his psyche deals with the experiments done on him when he was young, and is the ''best'' result of the known survivors.
* ''Manga/{{Naruto}}'':
** Subverted where Jinchuriki can attain great powers due to being linked to their Tailed Beasts. However, only Naruto and Gaara are explicitly shown using this trope due to their DarkAndTroubledPast, all the other Jinchuriki can use their Beasts abilities easily, these two just ''lose it'', manifesting when either are emotionally distressed or when their lives are at stake. [[spoiler: Both manage to reject or tame these circumstances, the latter turns his into a SuperMode. It turns out that the Tailed Beasts are just as intelligent as humans, and while they can be subjugated by a strong host, the key to ''fully'' utilize their power is to befriend them and become a team that shares a body]].
** Sasuke and the curse mark. During the Chunin Exams arc, Orochimaru gave him a curse mark, which, once activated, turned the quiet, elite loner into a sadist who broke a guy's arms without a second thought. Creepy! "You seem quite attached to these ''arms'' of yours."
* In ''Manga/NegimaMagisterNegiMagi'', it seems that [[spoiler:the "Encroachment of [[BlackMagic Magia Erebea]]" is causing Negi to develop one of these.]] Played with in that when he learns that [[spoiler: the Super-Powered Evil Side is a product of the Magia Erebea turning him into a demon and that there's no known way to stop it]], rather than decide he'll figure out a way to seal it away permanently, he ''instantly, without hesitation'', decides to get the whole [[spoiler: demonic conversion process]] over with right now and get it out of the way. Technically [[spoiler: he agreed without fully understanding how it worked, and Eva just [[SinkOrSwimMentor kickstarted the process.]] Given that the alternative is well, the same thing only over a longer time period, and that the point of the conversion is to get the Super-Powered Evil Side under control, it was really the only viable option anyway.]] More like a Super-Powered DarkIsNotEvil Side, really.
* Koyori in ''Anime/NurseWitchKomugi'' has a literal evil MagicalGirl SplitPersonality that she is completely unaware of.
* The main character of ''Manga/OPartsHunter'' is actually the container of Satan himself along with nine other demons that have the ability to possess people. There are also ten angels, none of which are evil or trying to take over but some are incredibly vain and judgmental.
* In ''Manga/OmamoriHimari'', [[spoiler:all demons, including Himari, can fall prey to their instincts or desires and become savage beasts. In Himari's case, she turns into a nigh unstoppable juggernaut--but, like any other demon, she runs the risk of not being able to return to normal.]] It's explicitly stated that in this situation, they ''will'' be exterminated.
* ''Manga/OnePiece'' has Chopper, a shapeshifter who normally has three forms available. When he eats a Rumble Ball, he gets access to four more forms for three minutes. If he eats another before the cooldown wears off, he gets three more minutes, but the shapeshifting is uncontrollable. If he eats a ''third'', he morphs into a giant monster that's incredibly powerful, incredibly resilient, and absolutely uncontrollable. In its first appearance, he [[CurbStompBattle one-shotted]] an enemy who had been beating him handily a moment before, then smashed through a castle wall and went on a rampage, destroying a dozen rooms before Franky managed to throw him into the ocean. [[spoiler: Chopper later masters this form (now officially called "Monster Point". He can use it by consuming a single Rumble Ball and retains full control, but is still too exhausted to move afterwards]].
** In the kingdom of Rommel, there was a phenomenon where it seemed as if the wind itself was cutting people. Eventually, a Marine warship was sent out to investigate, and the culprit was found to be a man by the name of Hakuba. Even to this day, he still hasn't been caught, but he still appears in towns where a certain pirate resides. The pirate in question? [[spoiler:Cavendish. In fact, Hakuba is the one who went out to sea to become the pirate named Cavendish.]]
* Pikachu in the ''Anime/PokemonTheSeries'' anime practically turned into a demon when he was [[spoiler:possessed by Groudon.]]
* Ryo Takatsuki from ''Manga/ProjectARMS''. His [[RedRightHand right arm]] is a nanite-based entity known as the Jabberwock. Get him ticked off enough, and the Jabberwock spreads over and takes control of his entire body. Though more really, really angry rather than outright evil, this doesn't stop Jabberwock from doing such feats as tearing apart a helicopter division, numerous other ARMS, emitting ''fire'', and much, much more, [[spoiler: said much, much more means he makes ''anti-matter'' on a whim later on in the manga. Oh yeah, and it evolves too.]]
* In ''Manga/{{Radiant}}'', Piodon removing the bandage on his cheek lets Seth access his Berserk Mode, turning him stronger at the cost of becoming feral and unable to differentiate between friend or foe. He gains some control over this form after training with Myr.
* Orson from ''Roleplay/RecordOfLodossWar'' is a Berserker Class and, when he gets angry, with the influence of the demon Hyuri he becomes an unstoppable killing machine that wields a massive claymore as if it were a toothpick.
* ''LightNovel/TheRisingOfTheShieldHero'' Due to the sheer amount of severe injustices thrust upon Naofumi right at the start of his so-called "Heroic Journey" it has accumulated into him evolving from his former [[NaiveNewcomer jovial-self]] to his internally-armored/cold [[KnightInSourArmor untrusting-self]], eventually having him unlock his '''Curse Shield''' (complete with [[RedEyesTakeWarning crimson eyes]]) that not only lets him exude his hatred upon those that wronged him, but to everyone else as well, as it is fully indiscriminate when he completely gives into it, and was nearly becoming a '''very''' deadly [[ProtagonistJourneyToVillain Hero-turned-villain]], just as everyone accused him of from the beginning thought he was... if not for his [[TrueCompanions true comrades]] there to snap him out of it before he could delve even further into its madness-imbuing embrace. If that wasn't enough, [[spoiler: the soul of the [[DracoLich Zombie Dragon]] he slain earlier with help of his party members, now resides within his Curse Shield, tempting him to give into his unfettered hatred and rage completely whenever he unlocks a new depth of its dreaded curse-fueled power.]]
* Moka's "super-vampire" side in ''Manga/RosarioPlusVampire''. Super-Vampire Moka speaks to her normal self through her Power Limiter, giving her guidance that she needs. This one isn't evil so much as very emotionally cold, though.
** Though recent chapters have revealed that Inner Moka is the true personality of the one body and the Outer Moka was created [[spoiler: when Moka's powers were sealed by her mother's Rosario so she could go in to hiding. Outer Moka's personality is actually based on her mother Akasha's personality.]]
** Tsukune's ghoul transformation is much closer to the trope. He requires a power limiter like Moka to keep it under control, but unlike Moka, he's a complete monster without it, and only monster of a similar/higher level to Inner Moka stands a chance against him, unless he ''really'' cares about them like his [[TrueCompanions friends]]. As of Chapter 41 it seems he's at great risk of becoming [[spoiler: a second [[SealedEvilInACan Alucard.]]]]
* Himura Kenshin from ''Manga/RurouniKenshin'' is a TechnicalPacifist in battle, fights with a reverse-blade sword and vowed years ago to never kill again. But if things seem to be getting out of hand even for him to handle (usually when his friends are in danger), his fighting style and mindset slowly begin changing into the highly pragmatic and ruthless Battousai, the assassin he was ten years ago. He switches the extremely humble ''sessha'' for the brash ''ore'', loses the ''de gozaru'' from his speech, his eyes turn gold and more slanted and he moves for the kill. In the anime, Battousai seems to be considered an actual personality Kenshin has learned to seal off by creating his rurouni persona - he has to punch himself in the face to push it back and revert back. In the manga, this gets lampshaded a bit when Kenshin remarks that his face muscles have cramped and he isn't able to end his permanent death glare.
** It's an unusual case, as in his current state Kenshin is actually much ''stronger'' than when he was the Battousai, having fully mastered Hiten Mitsurugi Ryu, including learning its ultimate technique, in the intervening years. But as the Battousai, he never held anything back, always going for the immediate kill. If he didn't stop himself every time the Battousai persona tried to emerge, though, he'd combine his increased strength with his former ruthlessness to become a near-unstoppable killing machine.
* In ''Manga/{{Saikano}}'', Chise's personality while in [[PersonofMassDestruction the Ultimate Weapon form]] could be psychotically vindictive, threatening on multiple occasions to utterly eradicate anyone who got in her way or made her mad, be it friend or foe... and that she could do so with ridiculous ease made her even more horrifying.
* ''Franchise/SailorMoon'':
** Hotaru Tomoe has ''two'' other sides. Sailor Saturn and Mistress 9, who nearly destroyed the world. Hotaru also subverts this trope. Sailor Saturn's breed of destruction is basically a cosmic ResetButton - albeit one that's only marginally better than outright annihilation. Mistress 9, on the other hand, is desperately weak; the Deathbusters' scheme in the second half of the season boiled down to saving her before she (and Hotaru) curled up and died.
** Also Chibi-usa, who had one as well when she was brainwashed by the Wiseman, known as the Black Lady.
* ''Manga/{{Saiyuki}}'':
** Son Goku. His 'evil side', the Seiten Taisei, is akin to a heretical chaos god and nearly overthrew the Heavens, goes on an UnstoppableRage whenever unleashed, and usually ends up trashing both the enemy, AND his teammates by the time he's finally stopped. The only thing that keeps him in check is the crown he wears which serves as a RestrainingBolt.
** Cho Hakkai's youkai form would normally just be a SuperMode, but when he changes into it he risks slipping into this due the Minus Wave that is sending youkai berserk. (And consequently, he doesn't pull it out unless the situation is [[GodzillaThreshold beyond dire]] and it's time to set his usual [[StepfordSmiler nice-guy facade]] aside, meaning that even without the Minus Wave there's going to be blood on the walls when he's finished.)
* Subverted in ''Manga/SamuraiDeeperKyo'': prior to his [[TimeToUnlockMoreTruePotential further training]] under his master Muramasa, Onime no Kyo was in fact ''weaker'' than Mibu Kyoshiro, who was merely [[ObfuscatingStupidity feigning weakness]] to complete the facade of a harmless medicine peddler.
* Lina from ''Manga/{{Slayers}}'' when she's [[spoiler:possessed by the being that accidentally created the universe and was presumed to be ready to undo it just as willingly. However, it is instantly subverted as it chastises the villain that made Lina fall to it and unmakes only him and all his plans. Her actual motivations [[BlueAndOrangeMorality are stated to be simply alien to our moral scale]].]]
* In ''Anime/SonicX'', absorbing the energy of a factory's worth of fake Chaos Emeralds coupled with seeing his friends tortured unleashed Dark Sonic for the first time in animated continuity. Complete with white eyes and navy-dark energy all over his body, plus the ability to tear anything that pisses him off to shreds.
* In ''Manga/SoulEater'':
** [[spoiler:Soul Eater]] is infected by some of Medusa's black blood, which manifests itself as a devil living inside his head [[DealWithTheDevil offering him power in return for giving in to the insanity]]. On the one occasion [[spoiler:he and Maka]] give into it in order to stand a chance against TheDragon, the trope is almost fulfilled to a tee... Except it's not so much a "Super-Powered Evil Side" as a "NighInvulnerable giggling lunatic side who catches TheDragon completely off-guard". [[spoiler:They ''barely'' make it back to sanity, which the devil seems to consider only a temporary setback.]]
** While not anywhere as drastic a change as the above, Stein's tactic against Medusa, of giving into his own madness, could also be seen as this. Though this side is not so much 'hidden' as it is what Stein would ''be'' if he didn't hold himself back through fear. He also seems able to control it frighteningly well, if Spirit's comments at the time are anything to go by.
* In ''Anime/SteelAngelKurumi'', at least the anime version, it's revealed that Kurumi's Angel Heart Mk. II has both an angel ''and'' a demon in it. Thanks to Nakahito commanding Kurumi not to hurt people, Kurumi finds herself helpless during fights because she doesn't want to hurt anyone, especially her fellow Steel Angel sisters. The demon side manifests soon after, BlankWhiteEyes, grim demeanor and the ability to punch holes into walls ''from a distance''. When Nakahito's kidnapped in an attempt to find out why his power makes Kurumi stronger, she starts to freak out and slip farther and farther into this power until everyone is forced to use a last-ditch weapon to kill her. Thankfully, Nakahito's able to break through to her and TrueLovesKiss ends up purifying her heart.
* Double-subverted (at least) in ''Super Taboo'' with [[NiceGuy Yuu]] turning into [[GoodEyesEvilEyes "Instinct Yuu,"]] which is less OmnicidalManiac and more the personification of AllGirlsWantBadBoys that's initially ''desired'' by his [[IncestIsRelative mother and sister]] since that side awakens whenever he's sexually aroused [[WhatDidIDoLastNight (minus everyone being drunk on Christmas)]] and implied to be [[LikeFatherLikeSon inherited from his father,]] whose [[CompellingVoice voice is even mesmerizing enough for Up To Eleven Phone Sex with his wife.]] Other than the confusing blackouts and [[MyGodWhatHaveIDone reactions to sleeping with various women]] it/he's harmless until [[TookALevelInJerkass getting too rough with his sister,]] requiring a BattleInTheCenterOfTheMind where Reason and Instinct (previously just a running gag where Instinct curbstomps Reason in cartoon-form ex. Barney-like dragon eating a knight) are personified as a BettyAndVeronica that he has to choose between despite EvilIsSexy. He finally chooses to be with Reason and rewarded with one last shot at his mom as himself (who's somehow a virgin) before being more steady with his [[BrotherSisterIncest sister as a happily ever after.]]
* In ''Manga/UFOBaby'', you can see a crystal-clear example in Christine, the older Hanakomachi... when a girl (human, alien, it doesn't matter) approaches her beloved Kanata in a remotely romantic way, she emits a black aura and her eyes glow: it's your cue to get away. In such a state she is capable of feats like lifting trees & breaking concrete walls. She's not evil, just [[ClingyJealousGirl clingy]].
* [[https://www.youtube.com/watch?v=Zf0uzEhbg88 This short cartoon]] about an anthro clione, whose SES is based on his real-life counterpart's mouth. [[https://www.youtube.com/watch?v=Kc50vlH6DJ8&NR=1 The sequel]] stars a female version with a dash of {{Tsundere}}.
* The protagonist of ''Manga/TheThreeEyedOne'', Hosuke Sharaku, is a tiny, wimpy, Charlie Brown-esque boy who turns into an immensely powerful, larger, psychic supervillain when the bandage on his forehead is removed, revealing his third eye.
* Vash the Stampede's eponymous weapon in ''Manga/{{Trigun}}'' is triggered involuntarily by such events.
** There is less "evil" here than "EvilTwin pulled the trigger" or occasionally "moment of UnstoppableRage." Vash has never shown a Super-Powered Evil Side, although he does have the related tropes of CrouchingMoronHiddenBadass, an EvilTwin, and the occasional burst of aforesaid temper, after he witnesses a massacre or something else heinous.
** Livio from the manga plays it more straight, actually having a split personality.
* ''LightNovel/TrinityBlood'': Father Abel Nightroad [[ObfuscatingStupidity only looks like a bumbling idiot]] most of the time -- in reality, he's an extremely powerful and extremely dangerous Crusnik, a super-vampire that preys on regular vampires. He voluntarily limits his power to 80% activated, at most, though, although he does suffer from SanitySlippage at that point. [[spoiler: His [[EvilTwin brother]], Cain, [[WithGreatPowerComesGreatInsanity was driven to insanity by fully-activating his power]], so yeah, that voluntary PowerLimiter is actually a good thing.]]
* ''LightNovel/VampireHunterD'': {{Dhampyr}}s (human/vampire hybrids) can 'vamp-out' under physical and/or emotional stress and start exhibit Noble-like traits such as drinking blood, etc. Given how powerful D is when he's ''trying'' to act mostly human, when his Noble side emerges, expect plenty of OhCrap moments and [[CurbstompBattle Curbstomp Battles]].
* Sumire's Anti-Virus mode (called "Berserker") in ''Manga/VenusVersusVirus''. It's brought on by being shot by a special bullet. Berserker Sunire is supposed to only hurt Viruses however she is attracted to Lucia as well.
* In ''Manga/ViolinistOfHameln'', Hamel's [[spoiler:mazoku blood]] gives him a Super-Powered Evil Side that, however, is not usually activated by rage or being near death, as it usually the case, but instead takes over whenever he cannot carry on anymore and is close to HeroicBSOD. It comes with demonic physical changes, such as horns and wings, is powerful enough to easily devastate whole cities, indiscriminately murderous and completely uncontrollable [[spoiler: until the final battle, when Hamel managed to stay in control despite the full-body mazoku transformation, because that time he fought for his friends and love and only transformed because the BigBad's power level was high enough to warrant it.]]
* In ''Manga/{{X 1999}}'', [[spoiler: BigGood Hinoto is shown to have one of these, who wants to unleash TheEndOfTheWorldAsWeKnowIt to become the only DreamWeaver.]] When the manga was given a NoEnding, [[spoiler: her Dark Self [[SplitPersonalityTakeover has completely taken over her]].]] This is dealt differently in the TV series, [[spoiler: where Hinoto goes through an HeroicSuicide to stop said Dark Self.]]
* When Manga/{{Yaiba}} loses control of the Raijin Sword he turns into a [[ShockAndAwe lightning-blasting]], destructive avatar of the God of Thunder.
* Yugi's powerful alter ego in ''Anime/YuGiOh'', Yami Yugi, is not actually evil, but he is a lot less concerned for the well-being of his enemies. Yami Bakura and Yami Marik, on the other hand, are both [[AxCrazy gleefully, psychotically evil]]. (Regular Marik isn't exactly a nice guy either.) In the manga, however, Yami is initially a GoodIsNotNice antihero who will dole brutal punishments out to the AssholeVictim of the week, the severity usually varying by threat but always a terrible MindRape at the very least. WordOfGod is that this due to millennia of imprisonment, but CharacterDevelopment and the influence of Yugi and co. put him in the GoodIsNotSoft category. This may have been the result of ''Manga/YuGiOh''! being planned as a horror series and Yami Yugi being a straight split personality originally. This trope comes into play during the Doma filler arc of the anime, when Yami Yugi showcased his vengeful, darker side.
** Judai (Jaden), Fubuki (Atticus), and Kaiser (Zane) in ''Anime/YuGiOhGX''... except Kaiser doesn't gain an evil side as much a [[FreakOut new evil persona]].
*** Fubuki is possibly unique among this trope in that he has, twice, ''purposely'' assumed it, and had a rather good reason both times (well, good in his view, maybe). The first time he thought it might bring Kaiser back to his senses, seeing as he thought Kaiser might have been under a similar curse. (It didn't work, seeing as that was not the case.) The second time was due to his feeling that bringing Darkness (Nightshroud) back was the only way to answer [[UnfinishedBusiness the questions]] tormenting him.
** Displayed in ''Anime/YuGiOh5Ds'' with the Dark Signers. Most of them became evil due to BlatantLies told to them by the Earthbound Gods, and most [[RedemptionEqualsDeath came to their senses before it was too late]]. Aki (Akiza) is another example, although a HeelFaceTurn in her case didn't cause her to lose her powers. (In fact, it actually made them more benign, eventually.)
** Yuya and his counterparts of ''Anime/YuGiOhArcV'' have what is known as "Awaken", in which their eyes glow and they become enraged and battle-thirsty in order to win a duel. Yuya develops one after absorbing his alternate dimension self, Yuto. It comes with glowing red eyes, a CreepyMonotone voice, and MajorInjuryUnderreaction to being repeatedly hit with a monster's flamethrower. The persona has given Yuya some powerful cards (notably Odd-Eyes Rebellion Dragon). But the more powerful it gets, the more violent and malicious it becomes.
*** Yuya actually has two established evil sides; Yuto, who while otherwise benevolent, will act on his ([[ThePurge completely]] [[WarIsHell justified]]) hatred of Fusion and Academia. The other is an unknown darkness that's [[SplitPersonalityTakeover trying to take over both Yuto and Yuya.]]
*** That unknown darkness living that's trying to take control of both Yuya and his counterparts? [[spoiler: That's the Devil Duelist, Zarc, whom Yuya, Yuto, Yugo and Yuri all used to be part of, until Ray split him, the universe and herself into four pieces each. Zarc eventually gains full control over Yuya and his counterparts and it's not pretty!]]
* In ''Manga/YuYuHakusho'':
** Parodied when Yusuke [[spoiler:dies, and it is revealed that he is in fact part demon. Said demon blood kicks in and he comes BackFromTheDead, with his demonic powers lending him a considerable increase in strength.]] He then decides to have a little fun at the expense of some alarmist commandos who wanted to take him out.
--->'''Yusuke:''' For what I desire is ending the world and everyone in it. For I am [[spoiler:the mighty Mazoku, Lord of Evil! And now, after hibernating for a thousand years I will finally reveal my true form!]] AHAHAHAHAHAHAHAHAHA... psych!! Damn, you guys are gullible!
** Late in his fight with Sensui, [[spoiler:the trope is played straight, as while he still isn't quite able to overpower him, his demonic ancestor Raizen takes control of his body and uses it 'better,' defeating Sensui easily and killing him, which Yusuke is not cool with. Mostly because he wanted to kill Sensui himself...]]
** Sensui himself is an inversion of this trope. Of [[spoiler:his seven personalities, the strongest one is Shinobu, the original one, and the only one to remain pure and innocent. His Kazuya personality, by far the most violent and sadistic, is the weakest personality shown.]]
** Kurama displays a variant on this trope in the Dark Tournament when [[spoiler: his opponent tries to reverse his aging to make him a baby, but goes too far and reverts him to his previous incarnation as a powerful demon bandit.]]

[[folder:Comic Books]]
* Astronaut Brice Rogers became the Moonman after passing through a comet's tail while traveling to the Moon. During the day he was Brice, but exposure to moonlight forced the emergence of his criminal alter ego.
* Anti-hero (but firmly one of the good guys) Hellhound in ''ComicBook/AstroCity'''s Dark Ages arc has a huge, colorful demon inside him. When it comes out, well, the demon isn't one of the good guys.
* Franchise/{{Batman}}:
** In the ComicBook/BatmanRIP storyline, Dr Hurt's mental attacks on Batman unleash a "back-up personality" Bruce had installed in his psyche, known as the "Batman of Zur-En-Arrh", who is essentially Batman without Bruce Wayne, i.e. completely unstoppable, but willing to do things the normal Batman wouldn't dream of to get results (including, it is implied, torture). Once again, more of a "superpowered" (he's still a BadassNormal) Id AntiHero side than truly evil.
** Two-Face is sometimes treated this way, [[BadGuysDoTheDirtyWork being able to do the nasty deeds]] that "good" Harvey Dent can't bring himself to. This is particularly evident in the story [[https://www.youtube.com/watch?v=sKPLopZt6b4&hd=1 "Two of a Kind"]].
** In an ''Elseworld'' story called "Batman/Etrigan: A Tragedy", Bruce Wayne is (unknowingly) the host of Etrigan the Demon, who emerges every night to violently battle criminals in Gotham. However, Etrigan is only as restrained as he is because of Bruce's virtue, and in reality, Bruce has been trapped with Etrigan for over a thousand years, pretending to be his own descendant unknown to himself because his servant Alfred (in reality Merlin the wizard), has kept watch over him and constantly changed his identity for all this time out of guilt of dooming him to an eternity as a prison for Etrigan. Bruce attempts to exorcise Etrigan, but the results are disastrous, resulting in the deaths of Catwoman, Killer Croc, Commissioner Gordon and several police officers, as well as Bruce's fiancee Glenda. Bruce consigns himself to repeating the cycle once more as Etrigan's jailer.
** In "The Third Mask", a story in the ''ComicBook/BatmanBlackAndWhite'' anthology series, Batman tracks a serial killer with some kind of split personality condition, including an alternate personality who's dramatically muscled and capable of superhuman feats of strength and agility. At the end of the story, Batman manifests his own similar alternate self to confront him.
* ComicBook/{{Eclipso}} has acted as this to various characters in the DC universe. Subverted in one ''ComicBook/BlueBeetle'' comic, where Eclipso invokes this by releasing Jaime's darkest fantasy of ultimate power to serve as her champion against Paco. This backfires when [[spoiler: this turns out to be a dentist, who is easily defeated. Jaime's deepest desire has nothing to do with power; what he wants is a stable career to help support his family.]]
* ''ComicBook/WonderWoman1942'': The Silver Age version of the ComicBook/{{Cheetah}}, Franchise/WonderWoman villain, was the violent split personality of a celebrity, Priscilla Rich.
* In ''ComicBook/{{Daredevil}}'' and related comics, Mary Walker is a sweet, innocent woman who has two evil personalities, Typhoid Mary and Bloody Mary, who have sole access to their super powers.
* Jackie Estacado in ''ComicBook/TheDarkness'' also fits this, and likes it during the early parts of the series, as it gives him more unique ways to kill people.
* ''ComicBook/DoomPatrol'' has Crazy Jane, a woman with severe Dissociative Identity Disorder, caused by sexual abuse by her father. When the alien Dominators detonated their gene bomb during the "Invasion" event, activating the metagene in thousands of humans, Jane was one of those affected. Jane has 64 different personalities, some good, some bad, and some neutral or inactive (the Jane personality has no powers). Among the evil ones are Black Annis (a violent, psychotic misandrist with blue skin and razorsharp claws and teeth), and "Daddy" (a giant copy of Jane's father made of insects, excrement and puzzle pieces). The Daddy persona was destroyed when Robotman entered Jane's psyche and helped her defeat him.
* ComicBook/{{Etrigan}} serves as this to his host Jason Blood.
* Star Sapphire, villain and LoveInterest of ComicBook/GreenLantern Hal Jordan, was similar, with Carol Ferris being unaware of what her alter ago was up to.
** The Golden Age Green Lantern also had a villainess who was an otherwise innocent woman's split personality, the first Thorn. Alan Scott would actually end up marrying the Thorn's good side, Rose Forrest, while she was using an assumed name. Unfortunately, the Thorn re-manifested and Rose fled for Alan's sake, and then later had to give up her children to protect them. These children were in fact Obsidian and Jade. Some time later Rose would have another child, Mayflower of the Force of July, but her father was never revealed.
* The ComicBook/IncredibleHulk is the canonical super-Hyde. The Hulk, over time, has been softened down from "evil" to "pure id". Not that that stops him from racking up the damage bill every time he shows up.
** Banner does have the Devil Hulk personality inside him, which is pure evil... possibly. ''ComicBook/ImmortalHulk'' makes it a little ambiguous, with the Devil Hulk (an AppropriatedAppellation) hating the human world, but being genuinely protective of Bruce and the classic, Savage Hulk, and being downright horrified by the [[GreaterScopeVillain One-Below-All]].
** As well as [[{{Jerkass}} Gray Hulk]] and [[WhatHaveIDone Guilt Hulk]] -- though Grey Hulk isn't really "evil"; he's another closer to "id".
** Bruce Banner's wife Betty Ross was once transformed into the villainous Harpy. Later she became Red She-Hulk, who's more TheAtoner, and currently is the Red Harpy, whose looks and mentality are a mix of the former two.
* In ''ComicBook/TheLeagueOfExtraordinaryGentlemen'', Hyde is this to Jekyll. He points out (true to the source material) that this was not originally the case. Quite the opposite: Jekyll was originally a big strapping fellow while Hyde was rather diminutive. The reason Jekyll is a pale and sickly shadow of his former self while Hyde is a big hulking brute now? Without Hyde, Jekyll has no drive, and without Jekyll, Hyde has no ''restraints''.
* J'onn J'onzz, the ComicBook/MartianManhunter, has a [[WeaksauceWeakness fear of fire]] for good reason. When he loses his fear of fire? He unleashes Fernus, the last Burning Martian who beat the entire ComicBook/JusticeLeagueOfAmerica at once and Batman needed to call ComicBook/PlasticMan in to help. [[ItMakesSenseInContext Yes.]] ''[[ItMakesSenseInContext That]]'' [[BewareTheSillyOnes Plastic Man.]]
* In the Creator/AlanMoore Retelling of the comic ''Marvelman'', ''ComicBook/{{Miracleman}}'', Kid Miracleman is the only survivor of a nuclear blast (he thinks) and stays in his superpowered form for years. In this form, but using his civilian name of Johnny Bates, he grows up. His moral code begins to erode because he is the most powerful man on earth and he has no one to tell him what to do. When Miracleman confronts him years later, he is the CEO of a computer company and a rather nasty piece of work. They fight, and he is forced to change back into a normal human ''child'' (His other self didn't age for ''years'' while in stasis) and left at an orphanage. There he is constantly bullied by other orphans, having to carry the dreadful knowledge that he could become more powerful than any of them, but he dare not because KM would start killing people. Then he is pinned one day, and some of the boys attempt to gang rape him, and this pushes him past the breaking point. The resulting awakening of KM results in the slaughter of the boys and a significant number of the population of London. Miracleman is forced to make him transform back into a human and end his life with a NeckSnap. In an [[StoryWithinAStory apocryphal story called "The Rascal Prince"]], a book read by followers of Johnny Bates who think he was a tragic victim tells a tale two ways: The revisionist version that depicts KM's meeting with an older woman as a flirty chaste romance, and as the RealLife version depicting [[NightmareFuel the rape of an unwilling victim]].
* The ''ComicBook/NewMutants'' [[ComicBook/IllyanaRasputin Magik]], way back when, was partially transformed into a demon by Belasco. Her "Darkchylde" side is intelligent but malicious, though almost powerless on Earth, where her magic doesn't work very well. In the end it took over her and nearly ended the world in a major Crossover Event.
** Legion from the same series was first introduced with a Super-Powered Evil Side in Jack Wayne, as well as a Super-Powered Jerkass Side (the pyrokinetic Cyndi). He usually has one or more evil personalities, except when they are temporarily merged.
** His father Charles Xavier also sometimes suffers from this trope. First, in a crossover mini-series with the Micronauts there was the Entity, a personification of his dark side. Later there was the supremely powerful Onslaught, who also contained elements of Magneto's evil side. Then there is Cassandra Nova, who combines this trope with elements of the evil twin and alien invader.
* In pre-Crisis on Infinite Earths continuity, Stacy Macklin appeared for several years in DC's Wonder Woman series. She made her final appearance in ''World's Finest'', inheriting Moonman's powers and developing an alter ego as Lady Lunar.
* ComicBook/{{Raven}} of the [[ComicBook/TeenTitans Titans]] has to maintain strict control over her emotions to the point of being TheStoic. If she doesn't, she runs the risk of manifesting the extradimensional demon side of her family tree and becoming DaddysLittleVillain. This is one of the major reasons Raven and Beast Boy have never been able to make a relationship work in the long run despite strong mutual feelings for each other.
* ''ComicBook/RisingStars'':
** Stephanie Maas/Critical Maas; The only normal in a town full of superheroes actually just shunted her super powers (including flight, strength, and creepy-puppetmaster mind control) into her secondary, psychopath personality.
** Incidentally, Critical Maas is undoubtedly the inspiration for ''Heroes''' Jessica/Niki, right down to [[spoiler:her history of abuse by her father]] and her penchant for calling her 'weaker' half 'little mouse'.
* ComicBook/TheSentry and the Void, from Marvel Comics, are this trope taken to its extreme. They manifested as alter-egos of a single person, representing the good and dark sides of humanity, respectively. The Sentry is a superhero and the Void is a supervillain, and in a slight variation on this trope, the Void is exactly as powerful as the Sentry, and occasionally kills someone for every person the Sentry saves.
** It was later revealed that [[spoiler: the Void exists because before becoming the Sentry, Bob Reynolds was a junkie who broke into a research facility looking for crystal meth and ended up drinking a serum that gave him the powers of the Sentry. He became addicted to that serum and the rush of being an admired and respected superhero, but deep down he was still a selfish, murdering junkie -- and this expressed itself through the Void.]]
** And ''later'' it was revealed that the Void [[spoiler:was in fact the Angel of Death]]. ComicBook/TheSentry is [[MultipleChoicePast kind of a mess]] - it doesn't help that he's a fully fledged RealityWarper, meaning that it's quite possible that his backstory genuinely does change whenever he thinks up a new one.
* ''ComicBook/SonicTheComic'':
** Super Sonic. In that comic's canon, the Chaos Emeralds are full of pure evil (as energy), rather than their neutral alignment as confirmed as video game canon by ''VideoGame/SonicAdventure''. Super Sonic came about by overexposure to the Chaos Emeralds, and as such... he's insane, and evil, sadistic, psychopathic... and equipped with the power of the Chaos Emeralds. When he split from Sonic and lost his powers he mellowed out, but returned to form when he got them back.
** Doctor Robotnik is also this to his former self [[FriendToAllLivingThings Dr Ovi Kintobor]], due to exposure to raw evil Chaos Energy.
** Sonic's AlternateUniverse EvilCounterpart King Sonic inverts this trope by virtue of his own Super Sonic self being pacifistic in nature.
* ''ComicBook/SpiderMan'':
** Mr. Negative takes this to a whole new level. [[spoiler: He was born when a synthetic drug split a man's personality in two - the pure good side became philanthropist Martin Li, while the pure evil side became Mr. Negative.]] Both fight with each other in an interesting way - Negative likes to corrupt all [[spoiler: Li's]] good deeds, while [[spoiler: Li]] helps people that suffer because of Negative.
** Curt Connors and Lizard are often portrayed this way. However, one RetCon claims that Connors was always in control of Lizard and let him out when life was too hard for him. He just keeps telling himself it's not true.
** Though not portrayed this way in the original comics, all subsequent portrayals of the Venom symbiote have made it out to be this, with even the comic book symbiote having been {{RetCon}}ned into a more malevolent entity.
* ''ComicBook/{{Supergirl}}'':
** In the ''ComicBook/RedDaughterOfKrypton'' story arc, Siobhan Smythe--who usually is the super-villain named Silver Banshee--let her Silver Banshee evil self out during her fight with Supergirl to try to hold her mindless friend back. Despite of her fears, she manages to keep her banshee side under control.
** In ''[[ComicBook/Supergirl1982 Supergirl vol. 2]]'' college professor Barry Metzer built a machine to kick-start his brain and body's evolution; but he developed an evil, ruthless split personality who took over.
* The third Black Knight Dane Whitman's first squire, Sean Dolan, suffers from this. As himself, he's a normal human [[PluckyGirl Plucky Boy]] and BoisterousBruiser-in-training who looks up to Whitman and wants to be a good sidekick. But when he makes the mistake of drawing Whitman's cursed sword, he turns into the demonic Bloodwraith who is willing to kill good and bad alike, cruelly mocks Whitman and his friends and can (literally!) level small countries. Sean spends much of the time afterwards trying to keep his evil side and addiction to the sword's influence under control and failing miserably.
* ''Franchise/XMen'':
** ComicBook/{{Wolverine}} has a tendency to lapse into a "berserker rage" while in close combat. In this state he lashes out with the intensity and aggression of a mindless animal and is even more resistant to psionic attack. Though he loathes it, he acknowledges that it has saved his life countless times. Of course, he uses it so often without negative side effects that the whole "evil side" part is something of an InformedFlaw.
** It's still not clear whether Dark Phoenix is ''ComicBook/JeanGrey'''s Super-Powered Evil Side or a variation on GrandTheftMe. (Whether Jean actually ''became'' Phoenix (and then Dark Phoenix) or was merely ''replaced'' by the Phoenix Force is in an almost constant state of {{retcon}}, so the confusion is quite understandable.) However, one thing remains the same: if you see her [[EvilCostumeSwitch green costume turn red]], you want to be in the next galaxy over. (That's NotHyperbole; she's responsible for the eradication of a whole solar system.)
** Angel has Archangel, the persona he developed after being experimented on by Apocalypse. Warren usually has wings and average healing powers. Archangel has razor sharp, retractable wings that launch out metal feathers that are dipped in his natural poison. X-Force had to call upon Archangel more than a few times, though he has since been extinguished, and Angel now possesses angelic metal wings.
** ComicBook/ProfessorX himself is has had this happen as he tends to repress every negative thought and emotion he experiences--which on three different occasions--the lead-up to the original ''Phoenix'' story, ''X-Mem vs. the ComicBook/{{Micronauts}}'', and "ComicBook/{{Onslaught}}"--taking lives on their own, with the evil personality being the BigBad of the last two stories.

[[folder:Fan Works]]
* Played straight in ''Fanfic/AhArchfall''. Even before he had his Archs, Jago was a competent fighter but when things got rough, he could us his dark power side, known as "Papa Jupiter". At his most basic level, Jupiter can boost Jago's fighting power to the point where he can plaster ten grown men. At the full extent of his powers, he is AT LEAST as powerful as either the Almighty One or Lady Hild (possibly more so). Unfortunately at this level of power, he has no problem with killing people, even those he cares about (though he prefers enemies as they tend to fight back). [[spoiler:As the story progresses, its revealed that Jupiter taking over is the only thing that Jago is REALLY afraid of. This is brought to a head during the Deity Games when he faces a mirror that reflects a person's worst fears as sees the result of what a fully unleashed Jupiter can do; he devastates the world, crucifies Lamb and Damascus, beats Lind to death with a rock and uses his knife to murder their infant son. The physic torment this causes is so great that it actually makes the mirror shatter.]]
* In ''Fanfic/TheBridge'', Monster X's Kaizer Ghidorah transformation serves as this. Monster X is a NobleDemon, while Kaizer Ghidorah is a bundle of hatred and rage. Monster X is roughly equal in strength to other kaiju like Godzilla and Gigan, while Kaizer Ghidorah can curb-stomp them.
* In ''Fanfic/ChildOfTheStorm'', Harry has a dark side that starts appearing after chapter 50. While not strictly another personality, it's certainly another side of him. According to Carol (who's had a look inside his mind), like all the experiences that should have screwed him up have been locked away in a box in his mind, constituting his dark side. It's [[TranquilFury frighteningly cold]], ruthlessly calculating, and while not explicitly more powerful, Carol describes it as TheUnfettered, while others describe it as being frighteningly reminiscent of a young Magneto. In one early appearance, it resulted in Harry putting an entire HYDRA assault team at his mercy and nearly forcing a PsychicAssistedSuicide after their leader took a child hostage, only being talked down by Jane. Then, a chapter later, it led to him telekinetically ripping Gravemoss' ribcage open and tearing his heart out (not that it had [[HealingFactor any long term effect]]). Unsurprisingly, [[BestFriend Carol]] [[MoralityChain keeps a close watch on him]], as Harry does on himself, being invariably horrified by what he's done when it sinks in.
** Towards the end of the first book, Harry's protection is revealed as a fragment of the Phoenix Force, and the start of ''Ghosts of the Past'' shows that he can tap into it. Considering the already mentioned dark side and that the Phoenix has taken him over to protect him, appearing in the gear of the Dark Phoenix and destroying everything in its way, this is rather worrying - while the Phoenix is broadly benevolent or at least, [[spoiler: Lily, the White Phoenix of the Crown,]] is, the power itself is a) morally neutral, b) incredibly volatile. As a result, Loki's fear is that that the two will combine and turn him into the Dark Phoenix. [[spoiler: This fear turns out to be entirely justified.]]
** Bucky's Winter Soldier persona functions as this. He's still got the same abilities and skills, the Soldier persona is just much more ruthless, focused, and economical.
* In ''Fanfic/TheDarkSideOfTheMirrorVerse'', [[spoiler:Mirror Twilight creates the same ManaDrain device as [[WesternAnimation/MyLittlePonyEquestriaGirlsFriendshipGames Human Twilight did]], which ends up draining mana from ponies at the party she's attending, including Mirror Tirek, resulting in it overloading and exploding (as she hadn't absorbed the World Mirror's magic to prevent such a thing from happening). This, combined with her bitterness, hatred, and envy of Princess Trixie, transforms her into Nightmare Spotlight. She promptly rips Canterlot apart to create a floating stage in the sky and [[WhosLaughingNow attempts to kill Trixie to get revenge for the wrongs she thinks Trixie has done to her]], planning to move onto everypony ''else'' she feels did her wrong. All publicly before all of Equestria on a live 'show' to finally get the respect she believes she's been denied all her life.]]
* ''Fanfic/DateAReLive'': This ''LightNovel/DateALive'' has both existing and new inverse forms.
* In ''Fanfic/TheDearSweetieBelleContinuity'', Twilight's research indicates that all alicorns are vulnerable to this if they swing too far to an extreme of [[AnthropomorphicPersonification the ideal or magic they are meant to personify]], explaining Nightmare Moon. It is also implied Celestia went through this during Luna's exile. [[spoiler:Cadance forms one, the Crystal Empress, once she learns of Shining Armor and Luna's affair.]]
* There are a couple among the children of Fanfic/TheEmiyaClan.
** Sakuya inherited part of the Angra Mainyu from her mother. Perhaps because of the diluted bloodline, it manifested itself as a slightly annoying second personality rather than a mad dark mode. The family calls them '''Yin''' and Yang to keep things simple. Yang is a bookish, modest, and generally reserved girl with mild YuriFan inclinations. '''Yin''' is an openly perverted, conniving, and slightly sadistic YaoiFangirl.
** Haru, [[OurVampiresAreDifferent by virtue of being a vampire]], has his Dead Apostle side. It's more of a berserk mode, but an alternate future version of him, DA!Haru showcases what it could have made him into if he ever let it get out of control.
** Touma's ten years of torture and experimentation before being rescued left him with a cold blooded alter ego called, [[TheDreaded ''The Ghost'']]. It isn't evil, but it has no moral inhibition, wiling to do whatever it takes to protect those he cares for.
** Mana Ryougi has her alternate male personality, MANA, as per her family trait. She hates being told what to do by anyone, including herself, so she mostly ignores him. [[spoiler: Until she has her DespairEventHorizon.]]
* [[spoiler:Count Logan is this for Beast Boy]] in ''Fanfic/TheEndOfEnds''.
* [[Anime/CodeGeass Kallen]] has one in the fanfic ''Fanfic/FairyWithoutWings''. [[spoiler:It's the [[HalfHumanHybrid Etherious side of her soul]]]].
* Taiga has a variation in ''[[https://www.fanfiction.net/s/11905736/1/Fate-Gamer-Night-SE Fate Game Night]]'' when she wields her shinnai, which she's stored all her negative emotions in (particularly hatred and anger), turning it into a pseudo cursed sword. Though it's main weakness is that while she does become far stronger, the shinnai contains only a finite amount of power; once her hatred runs out, she turns back.
* Played with in ''Fanfic/HarryPotterAndTheMethodsOfRationality''. Harry has what he calls a "dark" side, which is extremely good at plotting and seeing through plots... but that's it. Harry, who is familiar with this trope, is ''very'' put out when he discovers that it's no better at magic than him, and thus considers his "dark" side to be defective.
* In ''Fanfic/{{Heir}}'' by Na'hiel "Tom" [[spoiler: [[Franchise/HarryPotter the horcrux Voldemort]] accidentally made that resides in Harry's scar which has became sentient [[LimaSyndrome and very protective of his host]]]] is this for [[TheKidWithTheLeash Harry]].
* In the ''WesternAnimation/JackieChanAdventures'' fic ''Fanfic/QueenOfAllOni'', the re-emergence of Jade's Queen of the Shadowkhan persona and her StartOfDarkness that occurs because of it is what kicks off the entire plot.
* ''Fanfic/LeviathanMyHeroAcademia'': [[Manga/MyHeroAcademia Izuku Midoriya's]] quirk is the ability to transform into a titanic monster dubbed "The Leviathan" should he ever lose control of his emotions. The Leviathan is extremely powerful, flattening buildings with ease, but is completely and utterly uncontrollable. Izuku can give himself specific traits of the beast by moderating his emotions, but he's nowhere near as powerful as what a full transformation can do.
* ''Fanfic/TheMLPLoops'': PlayedForLaughs. In canon, Luna went DrunkOnTheDarkSide, rebelled against her sister Celestia, and was banished to the moon for a thousand years. Whenever a Looper ascends to alicorn for the first time, soon after there will be a "sisters loop" where the new alicorn takes the place of Luna, with Twilight taking the place of Celestia. No matter how hard they try, the first time they experience such a loop the new alicorn will go DrunkWithPower and have to be banished to the moon. Of course, this being Equestria, a lot of these dark sides are [[PokeThePoodle more than a little silly]]. Examples include "Hard Truth" (Applejack becomes obsessed with the entire country growing apples), "Danger Dash" (Rainbow Dash performs more and more pranks), "Party Pink" (Pinkie Pie won't stop throwing parties), "Flying Hatred" (Fluttershy suffers dangerous mood swings due to a curse), and "The Fashionista" (Rarity invades griffin lands in an attempt to open up more markets for her dresses). Big Mac is the only known alicorn who managed to avoid this fate on his first run, but then he hadn't actually ascended.
-->'''Twilight:''' Congratulations on joining the alicorn club, it helps if you've thought of your evil self beforehand.
* In ''Fanfic/{{Mirrored}}'' [[spoiler: while stuck in Voldemort's form]] Harry draws on the power of the [[spoiler: horcrux.]] Subverted because while the [[spoiler: horcrux]] gives him a significant boost it is acting in complete accordance with Harry's desires [[spoiler: [[DeathSeeker even the desire for Voldemort's death.]]]]
* In the ''Fanfic/PonyPOVSeries'', Princess Luna ''nearly'' reverts back into her [[MadGod Nightmare Moon]] form as a last ditch attempt to [[EvilVersusEvil stop Discord]], but manages to snap out of it. It's later revealed that at least some ponies have a similar Super-Powered Evil Side; Rainbow Dash nearly transforms before being calmed down at one point. Unfortunately, [[spoiler: nopony is around to calm [[BewareTheNiceOnes Fluttershy]] down when she snaps and she transforms into the RealityWarping {{Mad God}}dess named Princess Gaia, a WellIntentionedExtremist [[UtopiaJustifiesTheMeans who seeks to turn the world into a utopia]] by [[BrainwashingForTheGreaterGood brainwashing everyone into being happy]] and [[FountainOfYouth turning them into foals because she perceives them as being happier at that age.]]]]
** [[spoiler: It's revealed in "Playtime" that Princess Gaia was simply an illusion hiding her ''real'' Super-Powered Evil Side, the monstrous Nightmare Whisper.]]
** Luna explains the Super-Powered Evil Side thing a bit in "AJ's Dream": it's what happens when a single aspect of an alicorn (or being with a similar power, like a wielder of an Element of Harmony) consumes them and becomes the ''only'' part of them. Nightmare Moon was when Luna's night became the only thing that mattered to her and [[spoiler: Nightmare Whisper was when Fluttershy was consumed by her kindness]]. We're also shown possible Super-Powered Evil Side forms for Applejack (Nightmare Mirror), Rainbow Dash (Nightmare Manacle), and Pinkie Pie (Nightmare Granfalloon), though all of which are AlternateUniverse versions of the mane cast.
** [[spoiler: The final stretch of the Dark World arc introduces Nightmare Eclipse, an alternate-timeline Twilight Sparkle gone Nightmare after being consumed by the desire to make Discord suffer for what he's done, and thus created a GroundhogDayLoop to trap him in, deleting each world and rewinding time each time Discord is defeated so he can suffer some more... and not caring that she's casually deleting/killing millions of innocent ponies each & every time she resets the loop.]]
** [[spoiler: In addition, the end of the Mind Games arc sees Diamond Tiara transform into a Nightmare, but as a result of Discord's psychological manipulation and breaking of her spirit rather than a facet of herself consuming her. Her theme is Discord's brand of chaos, and she earns [[TabletopGame/{{Warhammer 40000}} a certain eight-pointed star symbol]] as her new Cutie Mark.]]
* The plot of ''Fanfic/ThePowerOfTheEquinox'' begins when Twilight Sparkle, trapped in the crystal caves beneath Canterlot, accidentally [[SealedEvilInACan releases]] from a black crystal [[TheHeartless the Entity]]. After it [[EnemyWithin takes root in her body]], she transforms into a darker and carnivorous mare who has new powers, like a powerful {{healing factor}} and phasing abilities, and she can create appendages and weapons from the black substance that's attached to her. Making a point of no longer being Twilight Sparkle, she renames herself as Dimmed Star. However, while [[TookALevelInJerkass more aggressive and aloof than before]], she still cares about her loved ones to varying extend, and the worst things she does are done when the Entity [[DemonicPossession takes control over her mind]]. Rainbow Dash lampshades this trope to Spike by saying that Twilight has "pulled a Nightmare Moon".
* ''Fanfic/ShadowsAwakening'': Jade gains a Shadowkhan form that she can [[HenshinHero switch in and out of]], which gives her an edge in battle. But the more she uses it, the more [[EnemyWithin The Queen's]] attempted [[TheCorruption corruption]] of her body and mind accelerates, being [[HeartIsAnAwesomePower kept in check by only the Tiger Talisman]].
* In ''Fanfic/TheShadowWars'' universe, a Nightmare can happen naturally or with the assistance of the [[DarkIsEvil Night]] [[LivingShadow Shadows]], horrible parasitic [[DemonicPossession possessors]] from a dying alternate universe.
* Dark Cupid gets more than he bargained for in ''Fanfic/{{Spellbound}}'' when he hits Chat Noir with one of his MindControl arrows. Since Adrien is half-fae, and his fae side is resistant to magic, the arrow merely suppresses his human side - the side that has recognisable morality and compassion and other such niceties like restraint. He proceeds to enjoy beating Dark Cupid to a pulp, and would have outright killed him if Ladybug hadn't intervened.
--> '''Faedrien''': Y''o''u ''ſ''h''o''u''l''d''n''’t ''h''a''v''e ''d''o''n''e ''t''h''i''s.
* In the ''Fanfic/TamersForeverSeries'', [[spoiler: Chaos is Takato's Super-Powered Evil Side, and the reason why pushing Takato's BerserkButton is a '''very''' bad idea]].
* In the ''Film/StarTrekIntoDarkness'' fic ''[[http://www.fanfiction.net/s/9344456/1/That-Was-A-Good-Fight That Was A Good Fight]]'' this happens to Kirk as a side-effect of [[spoiler: Khan's blood]].
* In the Death Note fanfic ''[[http://www.fanfiction.net/s/9644493/1/Zenith-Darkness-Reverie Zenith, Darkness, Reverie]]'', this is [[spoiler: Kira's]] purpose. [[spoiler: Although the "superpower" in question is Kira's utter lack of morality and the willingness to wield the Death Note. [[BrokenAce Kali is]] arguably the more intelligent/strategically capable personality.]]
* ''Fanfic/Zero2ARevision'' has the Digimon emperor being presented as Ken's dark side whenever he shows up as a result of Demon's Dark Spores. Later, in an attempt to stall the prevent the Digidestined from entering the real world and destroy his entire army [[spoiler: and to keep the Digidestined from evolving their Digimons so that he will remain at full power to combat [[EvilVersusEvil Demon]]]], Umbradevimon decides to corrupt Davis, using his own jealousy and hatred for TK against him with the help of the Touch of Evil as well as 15 black gears to create Darkheart, Davis's own evil self. Darkheart at first starts out as an obedient automaton whose only purpose is to keep the Digidestined on their toes under Umbradevimon's instructions. [[FromBadToWorse Unfortunately just as the Digidestined decides to enter the real world and leave some behind to stall him]], Demon inserts a Dark Spore to him which gives him a free will and becomes a sadistic psychopath hellbent on absorbing the Digidestined [[ForTheEvulz just because he can do it]] and [[CardCarryingVillain to become the greatest villain of all time]]. Umbradevimon's plan unintentionally [[GoneHorriblyRight works a bit too well]] as Darkheart [[KnightOfCerebus single-handedly managed to create the]] DarkestHour for the entire Digidestined a long time (13 chapters to be exact) before he finally gets taken down.
[[/folder]]

[[folder:Films -- Animated]]
* ''WesternAnimation/HeavyMetal'' segment "Captain Sternn". While under the influence of the Loc-Nar, Hanover Fiste grows into a mightily muscled hulk and smashes through all opposition in an attempt to murder Sternn. [[spoiler:Once everyone's gone, he turns back. Sternn then thanks him for getting him out of the trial... before shooting him out of an airlock in lieu of payment.]]
* In ''WesternAnimation/TheIronGiant'' the giant is pretty powerful on his own, but friendly. You do ''NOT'' want to push his BerserkButton however.
* Uni-Kitty from ''WesternAnimation/TheLEGOMovie'' is normally a GenkiGirl CloudCuckoolander. However, it's shown she has some pretty bad anger issues, and when sufficiently pushed she transforms into a demonic, red-furred version of herself that can fly and bite [[MechaMooks Micromanagers]] in half.
* ''WesternAnimation/MyLittlePonyEquestriaGirls'':
** Sunset Shimmer [[WesternAnimation/MyLittlePonyEquestriaGirls1 in the first film]] is a nasty person, but [[EvenEvilHasStandards she still has limits]]; she doesn't kill Twilight and she lets Spike go rather than trade him for the Element of Magic, when she has her chance. When she corrupts herself (with the Element of Magic) into a demon form, she has no such limitations and tries to fry Twilight and her friends without a second thought. She's [[HeelFaceTurn immediately remorseful for what she's done]] after being turned back, and in later movies is able to harness the power of the Elements without becoming corrupted thanks to ThePowerOfFriendship.
** At the climax of ''WesternAnimation/MyLittlePonyEquestriaGirlsFriendshipGames'', [[spoiler:Twilight Sparkle's human counterpart transforms into Midnight Sparkle after being pressured into unleashing the magic inside her magic-absorbing amulet. With this power, she blasts open portals to Equestria all over the place, with little regard for the stability of the non-magical human world. She snaps out of it thanks to Sunset Shimmer.]]
* The anime movie ''Anime/{{Tekkonkinkreet}}'' has the main character Black get saved [[spoiler:from space aliens by his own Super-Powered Evil Side known as "The Minotaur" which then tries to completely overtake him and show him the true power "The Minotaur" can unleash.]]
[[/folder]]

[[folder:Video Games]]
* In ''VideoGame/PuyoPuyo Fever'', Klug has one in Possessed Klug and Sig might have one in Dark Sig. But we do mean "Super-Powered" for Possessed Klug; he's not only a final boss, but some kind of demon king from long ago. He appears often due to, surprise, [[AssholeVictim Klug's]] AesopAmnesia of carrying a possessed book ''[[TooDumbToLive after it already possessed him.]]''
* In ''VideoGame/TheWorldEndsWithYou'', the BonusBoss is the Noise form of [[spoiler:Hanekoma]], and since he ''really'' kills you if you lose, it can be seen as this. The fact that, during the fight, he [[spoiler: spews his human form's inspirational phrases like battle cries]] could show that he's not quite in control.
* To an extent [[spoiler: Berserker Asura]] in ''VideoGame/AsurasWrath'' is this, and is also a OneWingedAngel transformation: It's something of a ShoutOut to the ''Manga/{{Naruto}}'' example above, as well as the ''VideoGame/DotHackGU'' movie's B-ST form. It helps that the guys that made ''Asura's Wrath'' make ''Franchise/DotHack'' and the ''Naruto Ultimate Ninja'' games.
* In ''VideoGame/AvengersAcademy'', Superior Iron Man is interpreted as this for Tony. He goes mad with power after one of Loki's spells goes awry.
* ''VideoGame/BlazBlue'': Mu-12, [[RedBaron the Sword of the Godslayer Kusanagi]], is this for [[TheCutie Noel]] [[ArtificialHuman Vermillion]]. In a twist of the usual formula, Mu is her ''original'' form, created to destroy Master Unit Amaterasu, the equivalent of ''God'' in this setting. A botching of her "smelting" process (as in the entire building and city she was in exploded) resulted in her being incomplete and developing her own personality. [[BigBad Terumi]] [[StrikeMeDownWithAllOfYourHatred invokes her transformation]] and completes the process, but she's saved by [[TheHero Ragna]] and later turns to tap into that power as a regular SuperMode.
* The Slayer from ''VideoGame/BaldursGateII'', a ten-foot tall spiky mass of pure murder that the protagonist can use and [[spoiler:results from channeling the power of Bhaal, the murder god who fathered the PC]]. An interesting example in that the Slayer seems to have [[spoiler:been part of the PC all along, and only surfaces when the PC loses their soul.]] Using it results in a reputation loss, except for scripted events that force you into it. Plus there's the whole thing about it [[HeroicRROD killing you]] ([[WeCannotGoOnWithoutYou and thus ending the game]]) if you stay in that form for too long.
* In ''Franchise/TheElderScrolls'' spin-off DungeonCrawler game ''[[VideoGame/AnElderScrollsLegendBattlespire Battlespire]]'', this is a trait of the Dark Seducers. Also known as Mazken, Dark Seducers are an intelligent race of [[OurDemonsAreDifferent lesser Daedra]] typically found in service to the [[OurGodsAreDifferent Daedric Prince]] [[MadGod Sheogorath]]. They are [[DarkIsNotEvil more humble and sympathetic toward mortals]], having less of a PunyEarthlings attitude toward them than most lesser Daedra. However, they are also known to [[IFightForTheStrongestSide Fight For The Strongest Side]], quickly switching allegiances if it becomes beneficial to them. The group of Dark Seducers fought in ''Battlespire'' betrayed their former master (a lieutenant of [[TheSacredDarkness Nocturnal]]) to side with BigBad [[DestroyerDeity Mehrunes Dagon]] when he promised them greater power. They were rewarded by being remade in the image of Dagon's own greed and treachery - becoming not only physically stronger, but also gifted with [[SuperMode powerful]] [[GoodWingsEvilWings bat-winged]] [[WingedHumanoid forms]]. In later appearances, they lack this form, but are still powerful and intelligent lesser Daedra akin to [[LegionsOfHell Dremora]] and [[LightIsNotGood Golden Saints]].
* Django, the gun-slinging hero of ''VideoGame/{{Boktai}}''. In the second game of the series Django is infected with vampirism and almost loses his soul before his half-brother Sabata purifies him with the Solar Pile. After this, Django eventually gains the ability to transform between human "Red Django" and vampire "Black Django." Though it might be argued that Black Django isn't that much more powerful as, despite his dark-based powers, he loses the ability to use all of Django's magic (gaining new spells only he can use) and is harmed by both rain and sunshine. In the third game, the transformation is changed to a "Trance" attack, where he becomes much more powerful, however the transformation only lasts a limited time, or until you leave the room.
* In ''VideoGame/BoxxyQuestTheGatheringStorm'', Anonymous learns a skill called “Hidden Depths” that lets him deal massive damage to an enemy, but then leaves him in a state of [[UnstoppableRage uncontrollable rage]] for the rest of the fight. This seems pretty incongruous with the rest of Anon’s skillset, until [[WhamEpisode Chapter 7]] when you learn that he’s actually [[spoiler:an amnesiac fragment of Legion, a shattered chaos god and the GreaterScopeVillain, and that using Hidden Depths means letting Legion’s will take over]].
* ''VideoGame/BreathOfFireIII'':
** Ryu can transform into the ultimate dragon, Kaiser. Its normal form ([[spoiler:the Infinity gene alone]]) is uncontrollable and Ryu will attack randomly (including his allies). Two other gene fusions allow it to be controlled, with one ([[spoiler:Infinity + Failure]]) significantly weaker than the "true" form ([[spoiler:Infinity + Trance + Radiance]]).
** Rei can transform into a weretiger when he rejoins the party after the TimeSkip; like Kaiser, Rei's attack power is vastly increased but he attacks random targets. He can be directed to the target of the Influence skill (learned from Boss Goblins).
** Any character who uses the Berserk skill gains a similar effect as the weretiger transformation, but the downside is [[SuperPowerMeltdown that it kills you in three turns]] unless you have equipment that averts death.
* Soma Cruz in ''VideoGame/CastlevaniaChroniclesOfSorrow'' is [[spoiler: the reincarnation of Dracula]], while Alucard is Dracula's son. The emergence of their Super-Powered Evil Sides are Alucard's greatest fear and Soma's bad ending. (Although they both are [[SuperpowerLottery pretty damn powerful]] as-is.)
* The Abomination in ''VideoGame/DarkestDungeon'' is a [[OurWerewolvesAreDifferent werewolf]] that has mutated even his human form into a HumanoidAbomination, but the character in question is afraid that "it" does things behind his back such as eating children or causing mayhem and lives in constant paranoia as a result.
* Emil from ''VideoGame/TalesOfSymphonia: [[VideoGame/TalesOfSymphoniaDawnOfTheNewWorld Dawn of the New World]]'' has Ratatosk mode, where he morphs from a [[TheWoobie Woobie-ish]] NonActionGuy into an ur-badass AntiHero BloodKnight. [[spoiler:It's not so much that Ratatosk is Emil's Super-Powered Evil Side; instead, Emil is Ratatosk's NonActionGuy side.]]
* ''VideoGame/DeathEndReQuest'' has Glitch Mode. Even when used as a standard SuperMode, it changes the user's personality in a specific way that differs depending on the user, and usually for the worse. The reason is eventually revealed to be that the buggies (the miniature Entoma that enable Glitch Mode in the first place) actually feed off of a specific emotion, preventing the user from feeling it. Typical access to Glitch Mode makes said emotion flow back into the user to an extent, which causes the personality shift (Lily's emotion is [[UnstoppableRage anger]], Al's is [[AngstNuke sadness]], Lucil's is [[LaughingMad joy]], Celica's is [[DespairEventHorizon despair]], and Clea's is [[CowardlyLion courage]]). However, if their particular emotion overloads, they glitch out unwillingly and potentially ''permanently'', lashing out at everyone around them with even greater levels of power. The only exceptions are Clea (who willingly overloaded her courage in order to stand a chance against a glitched Celica) and Shina (who doesn't overload at all). And ironically enough, Shina's is probably the scariest, turning her into an AxCrazy paradoxical sadist that both asks if an attack hurt (which it probably did) ''and'' goes into WhyWontYouDie fits. Thankfully for the cast, the "evil" part seems to have disappeared in ''Death end re;Quest 2''.
** Speaking of ''Death end re;Quest 2'', Mai is eventually revealed to be a descendant of an [[StoryBreakerPower extremely overpowered]] godlike entity known as Marbas. While in the GoldenEnding, she can use the powers that Marbas inhabiting her body grants her (like the ability to make people explode into LudicrousGibs just by waving her hand and modify the world mid-degrade) without any ill effects aside from giving her swanky new ProphetEyes, the DownerEnding (which isn't a Death End, mind you) has her so consumed with grief over the death of her friends that she simply ceases to ''care'', giving Marbas full control of her body. This results in her not only gruesomely killing the one that killed them, but eventually turning her attention to... ''[[TheFourthWallWillNotProtectYou you, the player]]'', calling you [[YouBastard a piece of shit]] for all the Death Ends you probably went out of your way to see, gleefully singing "murderer" at you, and then [[DealWithTheDevil offers to show you even more pain and suffering in exchange for you going into a]] MadnessMantra consisting of Marbas' words of prayer. ''Sheesh, Creator/CompileHeart!''
* Rozalin from ''VideoGame/Disgaea2CursedMemories'' manifests a Super-Powered Evil Side during the storyline when her seal is broken, which turns to be [[spoiler:her former life as Overlord Zenon, complete with both memories and power, back from the dead]].
** Mao from ''VideoGame/Disgaea3AbsenceOfJustice'' has a similar Super-Powered Evil Side that can [[spoiler:go on a complete rampage in one of the endings]].
** While not "evil" so much as mindless, Usalia from ''VideoGame/Disgaea5'' transforms into a berserk beast when she goes without curry for too long, as a result of Majorita's curse. [[spoiler:The love of her parents plus the release of her own mental and emotional burdens causes the curse to devolve into her SuperMode when they take an attack from Majorita meant to kill her.]]
** Also from ''Disgaea 5'', [[spoiler:Killia has an alternate form where he reverts to his past identity as the ruthless, destructive Tyrant Overlord Killidia, which he can temporarily postpone by consuming a whole meal... though by the end it stops being adequate, and he needs to eat increasingly larger portions to keep Killidia at bay. Coming to accept his past identity without giving in to his urges is what causes Killidia to ''become'' his SuperMode.]]
* It is revealed in ''VideoGame/DotHackGU'' that Natsume has a split personality: Her normal self is her cheery, slightly ditzy self while her other self is crazed, rampaging Pker known as The Edgemaniac. This is played for laughs.
** In the movie adaptation, Haseo's B-St Form. [[TheWorfEffect Even if all it did was make him look pathetic against the final boss...]]
** Haseo's Avatar, Skeith, is also portrayed as this, although Haseo usually does a better job of controlling him than normal for the trope. Skeith is ''seriously'' scary when out of control, his actions being the only thing in the games that actually seem to frighten Haseo.
* Hawke from the ''VideoGame/DragonAgeII'' "Destiny" trailer exhibits this, gaining RedEyesTakeWarning when he resorts to Blood Magic to CurbStompBattle the Arishok.
** Similarly, any time a Mage Hawke uses Blood Magic in-game, it could be seen as tapping into this.
** Anders has one in the Spirit of Justice, constantly having to fight to maintain control after his own anger corrupted it into a Demon of Vengeance. When he loses control, he gains GlowingEyesOfDoom, a [[EvilSoundsDeep Booming voice]], VolcanicVeins and a BattleAura.
* In ''VideoGame/DragonBallXenoverse'', the villains Towa and Demigra have the power to bestow a dark power-up (officially dubbed "Villainous Mode") as part of their attempts to alter history. Most of they time they give it to characters who are already evil, but this trope is played straight the few times they inflict it on the heroes. The most prominent example comes near the end of the game when Demigra takes control Future Trunks thinking that the hero won't be able to hurt his/her own friend; Trunks maintains enough control to ask you not to hold back.
** The Evil Empowerment continues in ''[[VideoGame/DragonBallXenoverse2 Xenoverse 2]]'', where the two most dangerous opponents under their influence are [[ButtMonkey Yamcha]] and [[FakeUltimateHero Hercule Satan]].
* In ''VideoGame/FalloutNewVegas'' we have Lily, a Nightkin who used to be a kindly old grandma before being mutated into a hulking blue monster. For the most part, she still acts like her old self, but all Nightkin suffer from schizophrenia. Lily's manifests as "Leo", a being only Lily can see who tells her to do bad things. If Lily is taken down to a quarter of her health, Leo will take over and go on a murderous rampage until every enemy in the area is dead. After witnessing this once, you can learn that she has been only taking half-doses of her medication because taking full doses makes it hard for her to remember her old, human life with her (now long-dead) grandchildren. You can convince her to start taking full doses (which will stop Leo's rampages but give her a drop in stats), or go off her meds entirely (which will boost her stats but make Leo come out at ''half'' health).
* In ''VideoGame/FairyFencerF'', performing a FusionDance with the [[GodOfEvil Vile God]] always results in this, whether it be due to the Vile God being in full control of the fused body or simply [[TheCorrupter corrupting the fusee's own personality]]. Both times this occurs, the result is the FinalBoss of the route.
* ''VideoGame/FightersDestiny'' has a clown character, and there's a cheat you can use which turns him into a werewolf.
* ''Franchise/FinalFantasy'':
** Vincent Valentine from ''VideoGame/FinalFantasyVII'' can transform into a variety of monstrous forms using his limit breaks. Possible forms include Frankenstein's Monster, [[AxCrazy Jason Voorhees]] [[HockeyMaskandChainsaw with a chainsaw]] and Chaos, the BigBad of the first game in the series.
** [[VideoGame/FinalFantasyVI Terra]]'s Esper form seems to be this in ''VideoGame/DissidiaFinalFantasy'', as when she goes into it during the plot, she suddenly loses control and ends up fighting the other heroes.
** From ''VideoGame/FinalFantasyXIV'' [[spoiler: you have Fray who is a part of you the ''player character'' in the Dark Knight quest line. He teaches you how to use the powers of darkness and your own negative emotions to brutally slay your adversaries, and his influence makes you more abrasive and quick to anger in your character's dialogue. [[DownplayedTrope Downplayed]] in that he isn't necessarily evil, but more of a manifestation of all of your frustration over the fact that for all of your Primal slaying heroics and general willingness to help the people of Eorzea with even the most mundane tasks, you're often rewarded with barely a thanks if you're lucky and [[UngratefulBastard jack squat]], if not [[NastyParty the Ul'dah banquet]] if you aren't so fortunate. He would rather get you to just leave the people to sort out their own problems instead of having to come crawling back to you to save them yet again, or whenever they need something to get done that they're unable to do for themselves. By ''Stormblood'' [[CharacterDevelopment Fray softens up and accepts the hardships that come with being a hero]] after seeing that others are willing to sacrifice themselves for Eorzea and the Warrior of Light.]]
* Happens sometimes in the ''Franchise/FireEmblem'' series.
** Lyon in ''VideoGame/FireEmblemTheSacredStones'' gains this as a result of tapping into the Dark Stone, in Ephraim's route. (In Eirika's route, the power within the Dark Stone outright [[DemonicPossession possesses]] him.)
** General Gawain [[spoiler:aka Ike and Mist's father Greil]] in ''VideoGame/FireEmblemPathOfRadiance'' was already the strongest swordsman in Tellius before he took up the Fire Emblem; afterwards, it made him outright unstoppable, and uncontrollably bloodthirsty, until his wife [[spoiler:Elena]] sacrificed herself to pull the Fire Emblem out of his hand.
** The [[BlackKnight Death Knight]] in ''VideoGame/FireEmblemThreeHouses'' turns out to be this for [[spoiler:Jeritza, manifesting for the first time in his teenager days when he was known as Emile. When his father decided to get Emile's half-sister, Mercedes, to marry [[BabyFactory for producing]] [[SuperpowerfulGenetics Crest-bearing offspring]], Emile slipped into a blind rage and [[SelfMadeOrphan killed him along with a good part of his household]]. Since that time he's been struggling with his Death Knight persona activating every once in a while and turning Jeritza[=/=]Emile into a nigh-unstoppable bloodthirsty killing machine. He can overcome it through [[LoveRedeems love and compassion of his support partners]] on the Black Eagles route (the only route he is playable on), and in his paired ending with Mercedes -- if she was recruited into the party -- he sheds it altogether, undergoing willing imprisonment as his [[TheAtoner atonement]].]]
* Playable characters Dante, Lucia, Nero, Vergil [[spoiler:and Trish]] from the ''VideoGame/DevilMayCry'' series all can transform into a demonic version of themselves with stronger attacks and health regeneration. In ''VideoGame/DevilMayCry2'' this becomes [[ItsEasySoItSucks easy]], with the characters' demon forms not being thrown back, halted or even slowed by enemy attacks.
* Elena's alternate personality Millenia from ''VideoGame/GrandiaII''.
* This is the reason the [[UglyCute quaggan]] have survived in the PostApocalyptic world of ''VideoGame/GuildWars2'' despite being {{Actual Pacifist}}s; actually manage to piss them off, and they turn into what is best described as a cross between an orca and a [[TabletopGame/DungeonsAndDragons bulette]], with absolutely no regard for their safety or collateral damage. And when they calm down, they'll apologize for it.
* Dizzy from ''VideoGame/GuiltyGear'' has a similar problem with one of her sentient wings. She's VERY powerful and unleashing her true powers causes her to lose control to her evil wing, Necro, whose motto is "Destroy everything!". With Dizzy being a FriendToAllLivingThings this really troubles her. Not that the other wing, Undine, is much better. Unlike Necro, she won't attack anyone who comes within reach randomly, but she ''will'' annihilate anyone she perceives as even the slightest threat to Dizzy without even a second thought... and her definition of "threat" is just a little bit too broad for Dizzy's tastes. Undine is the wing that unleashes Dizzy's version of Gamma Ray... that says it all. Oh, and her tail has a will of its own too and often eats anything within biting reach.
* ''VideoGame/JakAndDaxter'',
** Dark Jak from ''VideoGame/JakII'', which Jak aquired after being exposed to [[{{Phlebotinum}} Dark Eco]].
** And then they added a Super Powered ''Light'' Side along with Dark Jak in ''VideoGame/Jak3'', unlocked at a monastary around 40 minutes into the game. You use both to solve puzzles.
** ''VideoGame/JakAndDaxterTheLostFrontier'' gave one to Daxter as well, although the bunny-ears are not good for its badass credentials.
* ''Franchise/KingdomHearts'':
** The Anti-Form [[SuperMode Drive Form]] from ''VideoGame/KingdomHeartsII'' subverts this trope as it's actually a penalty form (at best AwesomeButImpractical) to discourage overuse of the Drive Forms; it can only be triggered randomly (chance determined by a hidden "Anti-Point" mechanic) or by activating any form but Final in battle with the ability Light & Darkness active. While Anti-Sora looks ''damn cool'', he's not actually much more powerful than Sora in terms of offense, and can do nothing other than attack solo in a blitzing frenzy of clawing, kicking, and firing dark energy blasts. The inability to heal, gain experience, or really do ''anything'' else makes this form a liability. Also, Sora takes 50% more damage while in this form and can't revert until the drive gauge expires or he leaves the level.
*** And like Jak, Sora also gets a Super Powered ''Light'' Side in Final Form, which is unlocked after [[spoiler:Sora's fight with Roxas]]. Like Anti-Form, it has to be triggered by chance when using other Drive Forms, but once unlocked, Final Form can be manually activated at any point, and also reduces the risk of Anti-Form with each use. In this form, Sora wears all-white and takes on an angelic theme with two Keyblades serving as wings as well as weapons.
** Riku, on the other hand, plays this trope straight in four of the games[[note]](in chronological order: [=KH1=], Chain of Memories, [=358/2 Days=], and [=KH2=])[[/note]], but primarily in ''VideoGame/KingdomHeartsChainOfMemories'' when you can play as him and "Dark Mode" is one of his key abilities. Interestingly, he no longer has one as of ''[[VideoGame/KingdomHearts3DDreamDropDistance Dream Drop Distance]]'', but only because his control over his dark powers has improved to the point where he can use them freely without transforming.
** ''VideoGame/KingdomHeartsIII'' plays it straight for Sora by allowing him to willingly transform into Rage Form as a situation command when [[CriticalStatusBuff his health is below 25%]]. It locks out his ability to use magic, items and summons as before, but gives him overwhelming power and speed to compensate. Additionally, Rage!Sora is capable of wielding a Keyblade, and has access to its own unique finishers, Limits and Shotlock. It will also mitigate any previous damage dealt to Sora by restoring him to full health upon transformation. Best of all, you can keep your party members who can also still heal you with their own abilities and items. This form is so powerful that Sora was able to critically injure Xehanort, who forcibly transformed him into this state by extracting his Light side, despite the latter having the χ-Blade and the full power of Kingdom Hearts at his disposal. According to Word of God, the difference between Rage and Anti is that Anti is a form Sora takes on when his heart is completely stained by darkness and is driven by instinct. Rage, on the other hand, is triggered by Sora's [[UnstoppableRage raw fury and anger]].
* Iori Yagami in ''VideoGame/TheKingOfFighters'' is normally amoral, and (judging from his winposes) has quite a few screws loose. Riot of the Blood Iori, however, has absolutely no sense of self-restraint and will attack anything on sight.
** Leona also fits this trope, sometimes even more perfectly than Iori, because she is in the "good side" while Iori can't decide himself; with some EmotionlessGirl spices added, though that said, she has smiled [[http://img694.imageshack.us/img694/7456/kof96ika35.gif once]].
* Rean Schwarzer from ''VideoGame/TheLegendOfHeroesTrailsOfColdSteel'' has a hidden power located near his chest that whenever he loses control of his own self, he ends up becoming a guy clad in evil aura and only knows to kill the opponent. The adults tell him to go master it already so that he can control it and use it for his own, which he manages to do in ''Cold Steel II''. By ''Cold Steel III'' however, he's losing control over it because it's growing too powerful and Rean becoming even more stressed out that the one time he doesn't want to lose control over it, [[spoiler:he ends up giving in to it and ends up slaying the beast that was holding back the curse of Erebonia.]]
* ''VideoGame/LegendOfMana'':
** SubvertedTrope with [[spoiler: Blackpearl]], whose powerful form is actually how [[spoiler: she]] was originally, before trauma-induced amnesia turned her into [[spoiler: Pearl]].
** [[spoiler: The Mana Goddess]] also has one, and this is the reason why the world is so messed up.
* Dark Spyro in ''VideoGame/TheLegendOfSpyro'' series is ExactlyWhatItSaysOnTheTin; Spyro's eyes turn white and his body gets covered in a flowing dark energy ([[ScrappyMechanic that has a habit of clouding up the camera when gliding]]) and gives Spyro the [[GameBreaker fury element]]. It gets triggered when Spyro is overwhelmed in sadness, anger, or just a plain ol' HeroicBSOD. However, in ''The Eternal Night'' you can flicker it on and off at will in NewGamePlus ([[ChangingClothesIsAFreeAction even in cutscenes!]]). He's shown to mostly have control over it though, as seen in ''Dawn of the Dragon''.
* The Fierce Deity Mask in ''VideoGame/TheLegendOfZeldaMajorasMask'' turns Link from [[http://images5.fanpop.com/image/photos/32000000/Young-Link-Majora-s-Mask-the-legend-of-zelda-32057969-420-630.jpg this]] into [[http://img2.wikia.nocookie.net/__cb20100124002042/zelda/images/2/2a/Fierce_Deity_Link.png this]]. It's given to Link by (a representation of) [[BigBad Majora's Mask]] itself so they can play a twisted game of tag. The mask is such a GameBreaker that you're only allowed to use it in boss rooms.
* So, in ''VideoGame/MarySkelterNightmares'', the Blood Maidens have the ability to go into a so called "Massacre Mode" ("Genocide" in the original Japanese version), which is ''kinda'' like one of these, making them far more powerful and aggressive when coming into contact with large amounts of Marchen blood. However, said monster blood, along with mental stress, builds up a form of corruption, and if it becomes too great, they will enter their ''real'' Superpowered Evil Side, [[TheBerserker Blood Skelter]], which makes them go ''completely AxCrazy'', communicating solely in pained screams and [[LaughingMad some of the most insane laughter you've ever heard]]. Good thing Jack's around to keep them out of it.
** Speaking of Jack, his Nightmare self in ''Mary Skelter 2'' gains a so-called "Ripper Mode", attained when his heart rate gauge fills up too much. The Marchen imitating his human self also seems to have it, turning its hair black and and implying that [[FridgeHorror Jack may have it even normally]]. Either way, this is especially bad, because 1) Nightmares are freaking strong already, and 2) the only thing keeping him from a FaceHeelTurn is a psychic link with Otsuu, but if he goes all Jack the Ripper, she very much risks going into Blood Skelter herself. ''[[SarcasmMode Well that's fun.]]''
* ''Franchise/MegaMan'':
** Zero of the ''VideoGame/MegaManX'' series gains several powerful new abilities when he is exposed to large quantities of TheVirus. When he is fully awakened by the Sigma or Zero Virus, he loses all of his emotions and his personality shifts to the that of a cold-blooded killer.
** ''VideoGame/MegaManBattleNetwork'':
*** ''VideoGame/MegaManBattleNetwork4RedSunAndBlueMoon'': When [=MegaMan=] takes enough damage to enter "Anxious" mode, he will gain access to incredibly powerful chips. If a single one is used, he shifts to Dark Mode, losing the ability to Double Soul, but getting access to 2 powerful chips per turn which can help him absolutely [[CurbStompBattle curb stomp]] most bosses and enemies with little effort. If used enough in succession, this mode can continue into following battles, allowing him to start with Dark Mode and the Dark Chips. If [=MegaMan=] turns dark enough from the use of Dark Chips, his dark side will appear after he is K.O.'d and start fighting. [=MegaMan=] regains control after a while. The fight against Dark Rock near the end does the same, using every chip the player had ever used, including Navi summon chips and Giga Chips, and also can use all the Program Advances you've performed up to the point you fight it. Unlike the player version, there's no warning when it uses them.
*** Chaos Shadow Soul in ''VideoGame/MegaManBattleNetwork5TeamColonelAndTeamProtoMan'' makes [=MegaMan=] completely invincible and uncontrollable as the AI attempts to duplicate the player's fighting style.
*** ''VideoGame/MegaManBattleNetwork6CybeastGregarAndCybeastFalzar'' introduces a new SuperMode for [=MegaMan=] called Beast Out. If the turn timer runs out while [=MegaMan=] is in this state, he can enter another state called "Beast Over". In this state he becomes invincible and any loaded Chips will be at double power, but at the cost of [=MegaMan=] going out of the player (and Lan's) control.
** In ''VideoGame/MegaManStarForce'' Pat has a personality disorder. He'll randomly go into an evil state named "Rey" and punch someone. This foreshadows him fusing with Gemini and becoming Gemini Sparks W and B.
* In ''VideoGame/MetalGearRisingRevengeance'', Raiden recovers from a devastating HeroicBSOD by tapping into his "Jack the Ripper" ChildSoldier personality, turning him into an AxCrazy [[TheBerserker berserker]] who takes joy in inflicting pain. After the ensuing fight, Raiden can use [[SuperMode Ripper Mode]] whenever his Blade Mode Gauge is full, increasing his attack power at the cost of constant Blade Mode Gauge drain.
* In ''VideoGame/MetroidPrime3Corruption'', Samus gets the ability to enter Hypermode, fuelled by the evil substance known as Phazon. Staying in this mode for too long corrupts her, leading to a NonStandardGameOver, specifically turning into another Dark Samus.
* ''VideoGame/{{Neptunia}}'':
** Some of the HDD forms have this going on, as it not only boosts the [=CPUs'=] power but also noticeably changes their personalities (even if they're admittedly not ''evil'' per se). Noire for instance becomes more brash and cocky upon transformation, Blanc meanwhile becomes more rage-prone and aggressive and Vert herself gets more aloof and haughty. Plutia in ''VideoGame/HyperdimensionNeptuniaVictory'' plays this more straight, becoming a full-blown sadist as Iris Heart who has no issues harming ''[[FriendOrFoe anybody]]'' physically, emotionally or ''[[BlackComedyRape sexually]]''.
** The Chaos forms from ''Chaos Chanpuru'' play this trope more straight than the above examples.
* Then there's the Slayer's {{Expy}}, the Ravenous Incarnation from ''VideoGame/NeverwinterNights2: Mask of the Betrayer''. The Spirit-Eater curse can grant some pretty incredible powers if you feed enough...problem being that the curse is, you know, a ''curse'' - an utterly empty blight upon the spirit backed by divine malice - and will overcome you, drive you insane, push you to devour the spirits of all you see in an animal frenzy, and finally obliterate you so entirely that even your soul is destroyed forever. Giving in to your hunger for spirits to get more power speeds up that process a ''lot''.
* In ''VideoGame/{{Painkiller}}'', when you collect 66 souls of enemies you killed, you transform into an unstoppable demonic killing machine. It only lasts for about 30 seconds but that's all the time you'll need to obliterate an area full of monsters just by ''looking'' at them.
* Every single main character in ''VideoGame/Persona4'' must be recruited by defeating their Super-Powered Evil Side, or more accurately, their ShadowArchetype: the embodiment of all the things about themselves they can't stand to admit. The shadows have grown immensely powerful out of all proportion simply because being denied makes them stronger; once accepted, they become much weaker and "tame."
** The series also gives us Black Frost--the horrific result of adorable MascotMook Jack Frost remembering he's supposed to be a demon after all and invoking ThePowerOfHate. The process apparently renders him awesomely more powerful... and much more evil. Unless you're playing ''VideoGame/DevilSurvivor'', in which case it turns him into a [[PungeonMaster Pun-spewing]] {{Magical Girl}}-esque [[ForGreatJustice warrior of love and justice]]. ...And just as awesomely powerful.
** ''VideoGame/Persona5'' has the traitor. Every Persona-using character has a costume which appears on their body when they enter the Metaverse. [[spoiler:The traitor has ''two''. One is a campy outfit styled after a "hero of justice", which he wears when summoning Robin Hood. This form has all the normal powers of a Persona-user. Should he switch to his other Persona, Loki, he'll change into a black, armoured outfit which adds a neck brace and helmet to the magical masks. This form has some abilities which most Persona-users definitely do not have, like inducing psychosis in a target and amplifying attack power massively in exchange for a defence drop. He's also a lot more open about how sadistic and angry he is when in this form, culminating in him using his powers on ''himself'' so that he can tear the protagonist apart with no remorse.]]
* It may not be on quite the same level, but in ''VideoGame/PokemonColosseum'', there's a random chance that a Shadow Pokémon might go into 'Hyper Mode' during a battle. The Pokémon in question will be surrounded by a black aura, and will do more damage - BUT. It won't be able to use any moves you've unlocked, it can't be healed, and it will also take recoil damage when it attacks. Thankfully, you can [[SayMyName call out to it]], which brings it back to its senses.
** A truer example would be Hoopa from the [[VideoGame/PokemonXAndY Gen VI games]], who has a compact "Confined" form and a monstrous "Unbound" form where its Psychic/Ghost typing changes to Psychic/Dark. The "Evil" part is more prevalent in the film ''Anime/PokemonHoopaAndTheClashOfAges'', where the Unbound side becomes an EnemyWithout.
** Flavor text implies that Mega Evolution forms tend towards this trope.
* ''VideoGame/{{Primal}}'' has its main character who personifies this when in any of her monster forms.
* In ''VideoGame/PrinceOfPersiaTheTwoThrones'', the Prince occasionally transforms into an alter ego with a bladed [[ChainPain chain]]-[[WhipItGood whip]] (and [[PossessionImpliesMastery the skills to wield it gruesomely, out of nowhere]]) and who can completely regenerate whenever exposed to the Sands of Time, but at the expense of constantly deteriorating health otherwise. The Dark Prince is also a sociopath with a massive entitlement complex. Even when in the Dark Prince body, the Prince remains in control, but the Dark Prince hints that the health draining out of you is actually going into it, and that dying of this will give the Dark Prince control of the body (and, incidentally, Babylon).
* From ''VideoGame/LaPucelleTactics'', [[spoiler:Croix has his Super-Powered Evil Side as the Dark Prince serving the fallen angel Calamity.]]
* Jaster Rogue in ''VideoGame/RogueGalaxy'' does this, although his "evil" side isn't so much evil as so far above everyone else that he [[IgnoredEnemy barely notices they exist]]. Hard to tell the difference from the "normals" point of view, though.
* Johnny Garland gains this far into the third ''VideoGame/ShadowHearts'' game. [[spoiler:Johnny actually died at a very young age along with his sister, Grace. Their father managed to get his hands on the series' {{Tome of Eldritch Lore}}, in hopes of resurrecting them. He only succeeds in reviving Johnny, as his sister gives up her humanity in order to save him, leaving her an empty shell, "Lady". Because Johnny's body is composed of both "Malice" (negative energy) and "Will" (the human soul/spirit), after being fatally wounded by Killer, his "true" Malice form, the Awaker, emerges.]]
* The hero of ''VideoGame/ShiningTears'' is normally a timid amnesiac with a dislike for fighting, but when somebody else puts on the other matching ring of power he turns into two super-powered sides, one is a moral knight of justice while the other is an insane OmnicidalManiac BloodKnight.
* ''VideoGame/SonicTheHedgehog'':
** Sonic has one in ''VideoGame/SonicUnleashed''. At night, he'll turn into Sonic the Werehog, a bulky werewolf-esque form of himself with super strength and stretchy arms. Though his personality remains more or less the same except for the obligatory howling. This exception is {{lampshaded}} after it is revealed that [[spoiler:Chip is actually Light Gaia, a benevolent spirit, who is guarding the earth]]. Sonic then asks, if it could be Chip who keeps him from succumbing to Dark Gaia and becoming evil when in Werehog form, to which Chip replies that he has nothing to do with him, it's Sonic's kind heart alone which lets him keep his sanity.
** ''VideoGame/SonicAndTheSecretRings'' introduced the Darkspine form, which Sonic transforms into by using the World Rings of [[UnstoppableRage rage]], [[ThePowerOfHate hatred]] and [[AngstNuke sadness]].
* ''VideoGame/SoulSeries'':
** In the early ''Soul Calibur'' games, Nightmare was supposedly a Demonic-Sword-induced version of this for Sigfried. The latter freed himself in [=SCIII=], but his armor and residual evil power was [[EnemyWithout too attached to Soul Edge to die]].
** Two far more definitive examples show up in ''[=SCIII=]'' as the boss [[NightmareFuel Abyss]] (spawned from Zasalamel's quest for the power to die), and bonus boss [[SNKBoss Night Terror]] (Nightmare on 'roids).
* ''Franchise/SpiderMan'':
** As said in comics, any game that has the option of the black suit has it as this. In games such as ''Spider-Man 3'' and ''VideoGame/SpiderManWebOfShadows'', his attacks become more violent and aggressive, usually with CombatTentacles and spike tendrils.
** Subverted in ''VideoGame/SpiderManShatteredDimensions'': the Ultimate Universe Spidey (who is bonded with the symbiote again) is the kindest of the Spideys, though he possesses a "rage mode" in which he becomes more scary looking and his attacks are more devastating. His comments are actually the opposite, however, and he'll say things like "Yeah, let's have some good old fashioned RAGE!" and "Raaage! I'm not actually angry, I just like saying it." But it's justified, since Madame Web is using her powers to keep the suit from taking over.
* The Terror Mask in the ''VideoGame/{{Splatterhouse}}'' series embodies this trope, especially in ''Splatterhouse 3'' where its own personality, and its effect on Rick, become more apparent.
* In ''Franchise/StarWars: VideoGame/TheForceUnleashed: Ultimate Sith Edition'', you go into the ruins of the Jedi temple and eventually fight your Super-Powered Evil Side.
* Ryu, from the ''Franchise/StreetFighter'' series, has a power inside of him known as the Satsui no Hadou, or Surge of Murderous Intention, which he works to suppress and was retconned as the reason that Sagat received the scar he bears on his chest. Akuma (Gouki in the Japanese version) represents someone who has fully given in to the Satsui no Hadou, and when he's not holding back, he is truly fearsome. In ''Street Fighter Alpha 2'' and ''3'', Evil Ryu is actually a secret, playable character (a dark-skinned, red-eyed version of Ryu with some additional attacks that were borrowed from Akuma).
** Ryu's Super-Powered Evil Side is a result of his being unable to control the power. However, since the power still involves a willingness to kill and a more brutal mindset even when in control, he makes no effort to even try to learn how.
** Evil Ryu returns to the ''SF'' storyline through ''Super Street Fighter IV'', where he's a playable character. This time he has gone from merely a dark-skinned, red-eyed Ryu to a borderline PersonOfMassDestruction with a kanji carved on his flesh and a glowing orb where his heart should be. [[spoiler:Making Evil Ryu return to the surface was a plot point in the ''Ties that Bind'' tie-in anime. It almost works.]]
** Oni represents this to Akuma. Whereas Akuma does have some degree of control over the Satsui no Hado, Oni is Akuma when the Killing Intent finally consumes him. Oni drops the moral code of only fighting worthy opponents that Akuma held to, and will fight, and even kill, anybody and everybody he comes across. Oni is the one thing Akuma ''doesn't'' want to become. And the most terrifying thing is that Oni is miles above most other fighters, with only a handful including ''Cody and Gouken'' able to challenge him.
* ''VideoGame/TheSuffering'' initially plays this straight with a "primal form" that shreds enemies but damages your KarmaMeter. However, it's subverted twice over. First, you learn that [[spoiler:you're merely "under the delusion" that you turn into a monster when you go berserk]]. Then, the final boss proposes to "cure you"--and it sort of works. In the sequel, you can transform without harm, even if you're playing as a good guy.
* Queen Arshtat Falenas in ''VideoGame/SuikodenV'' took the [[BlessedWithSuck Sun Rune]] into her to prevent it from falling into the "wrong hands." Ever since, she [[PurpleProse melodramatically rants]] and [[NoblewomansLaugh cackles authoritatively]] whenever her "divine rule" is threatened. Once, she even unleashed the Sun Rune, completely dessicating a lake and its nearby landscape and leaving her nearby subjects to die a wasting death. All in all, a Super-Powered Evil Side is a great way to balance TheHighQueen and her [[GodSaveUsFromTheQueen darker counterpart]], leading to a natural [[TheWomanWearingTheQueenlyMask aloof regality]].
* In ''VideoGame/SuperSmashBrosBrawl'', some of the Final Smashes have this effect.
** Bowser's Final Smash transforms him into the ''even more'' monstrous Giga Bowser. Whether or not Bowser was evil to begin with [[DependingOnTheWriter depends on the game you reference]]...
** Luigi's Final Smash, according to its trophies, is "a reflection of the DarkSide he embraced in his brother's shadow."
* The God of War Melqart in ''VideoGame/TearsToTiara2'', who [[TheHero Hamil]] summons to take possession of his body by promising the blood and destruction of [[TheEmpire The Holy Empire]]. Ennead and Monomack describes the technique as going berserk. At the Ba'al festival, Melqart wipes out an entire squad of Golmes in one blow, [[AxCrazy fights without concern for collateral damage, laughs as he effortlessly deflects fire arrows of imperial soldiers, and forgets all about protecting Tart]] until she sings. Not that she was actually in any danger by that point.
* Almost every member of the Mishima family in the ''VideoGame/{{Tekken}}'' series is affected by the Devil's Blood, a curse that while it makes them stronger and grants them demonic powers, at cost of their humanity. Also Ogre/True Ogre.The Devil's blood affects the personality of those inflicted, and it's virulent where the host struggles to keep control.
** Devil Jin is esentially Jin Kazama overcome by the Devil Gene, unlike his human form, he's ruthless,cruel and sadistic, enjoying seeing his foes suffer, his alter ego, Jin Kazama tries at all costs to prevent the Devil's blood to take control.
** Kazuya Mishima was originally stricken when he thrown off the cliff by his father in order to survive, originally Kazuya was a good man with a kind heart, but the Devil's blood slowly consumed him, until Jun Kazama awakened in Kazuya his good side that fought off his demonic side. After Tekken 2, though, Kazuya's good side is suppressed by the Devil's blood and Kazuya made an agreement with it and he's able to control the form as he pleases. A shred of his humanity can be seen in his T5 ending where he defeats his grandfather and holds him in his arms, smiling at him and remembering his few happy childhood moments, before the Devil's blood takes control and kills him.
** Heihachi Mishima is just that evil, [[BadassNormal he doesn't need an evil side to get more evil, super powered or kick ass]].
** Jinpachi, who is affected by the Devil's blood, turned into a demon after he died underground under Hon-maru, imprisoned by his son Heihachi, after the events of Tekken 4 Jinpachi is released, and he holds the King of Iron Fist Tournament 5 to find somebody to stop him, as he could feel the Devil taking over. He also sends a letter to Wang, his old friend, to have a go as well.
** [[TheHero Jun Kazama]] counts as well. Turns out she's Unknown, a superpowered... well, where she sits on good and evil hadn't been established, but she basically turns into ComicBook/{{Venom}} and becomes a little more dangerous.
* In ''Tower Of Fortune'', The protagonist automatically transforms into a hulking, angry giant at 100% rage, with an 80% chance to hit (as opposed to the usual 45-65% range) and vicious, bloodthristy attacks from punching to sonic-screaming to pouncing on them and ripping their throats out with each subsequent hit. You can abstain from this mode with some skills or prolong the fury with others. How and why your otherwise generic warrior can become a were-giant is a mystery explained in the prequels.
* In ''VideoGame/{{Undertale}}'', there are two examples:
** The PlayerCharacter, The Human Child/[[spoiler:Frisk]] has two, the first is [[spoiler:The Fallen Child, the spirit of the game's GraterScopeVillain]], the second is ''you'', not [[spoiler:The Fallen Child]], '''you''', the person playing the game, should you embark on the more malevolent routes and ''specially'' Genocide, due to the game intense Meta nature, that's right, in ''Undertale'', YOU are the Super Powered Evil Side. Don't you feel special?
** Asriel is a PosthumousCharacter in the backstory who [[spoiler:was the NiceGuy crown prince and son of Toriel and Asgore. After dying tragically, they found themselves brought back as a [[TheSouless souless]] [[OurGhostsAreDifferent ghost]] possessing a golden flower, but because of said soulessness, they eventually degenerated into TheSociopath known as Flowey.]]
* At one point in ''VideoGame/WildARMs2'', Ashley is transformed into some kind of zombie-like creature early on, but before he is taken completely, he makes it to the [[OnlyTheChosenMayWield Argetlahm]] and pulls it out -- this has the result of countering the demon within him with the good force of the sword, and the resulting combination is a badass black-armored-red-trimmed entity called Knight Blazer. He can't actually use it in battle until a few plot points later, but once he gains the ability, nearly every remaining boss fight in the game boils down to letting him transform in order to open up a can of whoop-ass. [[spoiler:At one point, in a moment of UnstoppableRage fueled by [[HeroicResolve a terrorist threatening his girlfriend]], Knight Blazer actually [[TookALevelInBadass takes another level in badass]] and transforms into a gold-armored knight with extra abilities that is that much more powerful. And then at the end of the game, the "demon" portion escapes Ashley's body and reveals itself to be the EldritchAbomination responsible for devastating the world centuries ago, Lord Blazer. This leaves Ashley with the holy sword. Guess who wins [[ThePowerOfFriendship the]] [[ThemeMusicPowerUp resulting]] [[SugarWiki/AwesomeMusic boss]] fight.]]
* In ''VideoGame/{{Xenogears}}'', one of the primary villains for the first half of the game, Id, [[spoiler:turns out to be an alternate personality of the primary hero, Fei. Id was completely different from Fei in appearance (except for the face itself) and had several magnitudes more power than him. Shown in a flashback to defeat a half dozen [[HumongousMecha Gears]], unarmed, with a single hit each.]]
** When Id manifests, [[spoiler:even ''[[HumongousMecha Weltall]]'' gets a Super-Powered Evil Side, transforming into Weltall-Id.]]
** This is subject to the variation mentioned at the top of the page. Even though Id doesn't get as much screen time as his alter-ego, [[spoiler:Fei is a personality built on top of Id and the Coward (the original personality). Id is able to access the memories of the Contact, which Fei is only able to do near the end of the game.]]
** Grahf plays this role in two ways. [[spoiler: He is the metaphysical alter-ego of Lacan, a previous incarnation of Fei, and the (current) physical alter-ego of Khan Wong, Fei's father.]]
* ''Daze Before Christmas'' has a power-up that can turn Santa into a monster.
* ''VideoGame/GianaSistersDS'': Strongly implied by the credits. Punk Giana can bust blocks, shoot fireballs, and survive a hit, compared to Normal Giana... who can do none of those things.
* In ''VideoGame/TwistedWonderland'', magic users who either accumulate too much [[TheCorruption blot]] or become overwhelmend by their negative emotions will Overblot, where their magic increases in power, a GuardianEntity appears before them, and they act in an uncontrollable, destructive manner. If they aren't defeated in time, the Overbotted person may irreversably turn into a monster. [[spoiler:This event happens to a member belonging to each of Night Ravens College's dorms, all but one of them being the dorm heads]].
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* In ''Literature/SkulduggeryPleasant'', Darquesse and Lord Vile are the superpowered evil sides of [[spoiler: Valkyrie Cain and Skulduggery Pleasant]], respectively. Darquesse is [[spoiler: Valkyrie's]] True Name, and using the incredible powers that come from knowing her True Name [[DrunkOnTheDarkSide enhances all of her negative personality traits]] and causes her to revel in the death and destruction, seeing everyone else as ants to be crushed at her whim. Lord Vile [[spoiler: was created when Skulduggery first came back to life and fell into despair over the death of his wife and child. Being undead]] unlocked and enhanced his latent potential for Necromancy, and he became little more than a killing machine serving under Mevolent. He eventually came to realize the monster he'd become and hid away Lord Vile's Necromancy-infused armour, but [[spoiler: being trapped alone in the Faceless Ones' realm for a year]] weakens his resolve to keep Lord Vile locked away.

* Multiple examples in the ''Literature/SkulduggeryPleasant'' books. [[spoiler: Darquesse, Lord Vile and Shudder's gist come to mind]].

** And Yu's (Yuya and his counterparts) of ''Anime/YuGiOhArcV'' have what is colloquially known as Berserk Mode, in which their eyes glow and they become enraged and battle-thirsty in order to win a duel. Yuya develops one after absorbing his alternate dimension self, Yuto. It comes with glowing red eyes, a CreepyMonotone voice, and MajorInjuryUnderreaction to being repeatedly hit with a monster's flamethrower. The persona has given Yuya some powerful cards (notably Odd-Eyes Rebellion Dragon). But the more powerful it gets, the more violent and malicious it becomes.

*** That unknown darkness living that's trying to take control of both Yuya and his counterparts? [[spoiler: That's the demon, Zarc, whom Yuya, Yuto, Yugo and Yuri all used to be part of, until Ray split him, the universe and herself into four pieces each. Zarc eventually gains full control over Yuya and his counterparts and it's not pretty!]]

* Dark Jak from ''VideoGame/JakAndDaxter'', after being exposed to [[{{Phlebotinum}} Dark Eco]].
** And then they added a Super Powered ''Light'' Side along with Dark Jak in ''VideoGame/Jak3Wastelander''. You use both to solve puzzles.

* ''WesternAnimation/MiraculousLadybug'''s third season features an episode called "Cat Blanc" ("Chat Blanc" in the original French), which depicts a BadFuture in which Cat Noir is Akumatized into the titular villain. He somewhat subverts the trope by being insane and desperate to fix the damage he created by accident, desperate to the point of being willing to kill Ladybug and destroy the universe and PutThemOutOfMyMisery, but fits the "Superpowered" side of the trope to a T. Cat Noir's destructive powers are formidable to begin with (he once destroyed an entire PocketDimension in a previous episode), but his first act as Cat Blanc is a blast of destructive energy that cut the moon in half and decimated all of Paris with the recoil alone. This includes the villain Hawk Moth, who probably [[DidNotThinkThisThrough didn't consider the ramifications of deliberately traumatizing his own son and then giving him "unlimited powers of destruction"]].

* ''Anime/CodeGeass'': Lelouch's ThenLetMeBeEvil moment at the end of the second season where he [[spoiler: Geasses all of the army guys to become his personal slaves]] showing if he was to be evil he would be a complete monster. [[spoiler: Completed by him taking over the world]]