This Is Your Brain on Evil

"You think I've not tried to stop - to stop tying? I'm hooked! It's a habit with me now! Oh, boo-hoo-hoo! I swear to you: after I tie up this one defenseless woman, I'm going to swear off, so help me!"

— Snidely Whiplash, Dudley Do-Right

So you've just performed a Face–Heel Turn. Maybe you gave in to your Superpowered Evil Side, or you experienced a Freak Out, or you have your first shot of real power and see what having such control and influence can get you in life. Whatever the case, you've just taken your first taste of the true joys of evil, and it tastes good. You become enthralled, never turning back to your old ways (and shun off all attempts by your friends to do so), and are living the high life, loving every sadistic moment of your new existence.

Then, you feel it: a straining in your head, a dagger-like pain in your chest, a feeling of queasiness or disorientation, or some other physical malady. Or you realize you've become incredibly cold and antagonistic toward your friends and loved ones, followed by a feeling of being out of control with your own actions. Something is wrong; you never expected this to happen, and if you don't find a way to stop it, it'll ruin your relationships, kill your career, or — in the most extreme cases — drive you into an early grave.

Congratulations, This Is Your Brain On Evil. Since evil is often depicted as being a tantalizing and corrupting influence, it's just as often used as a euphemism for another, similarly tantalizing and corrupting, influence: drugs. Just like drugs, the side effects are all there: addiction, withdrawal, uncontrollable behavior, and, eventually, health problems and death. Usually, when a character is thrust into this trope, they get into it only knowing or caring about the positive, "feel-good" parts of the power or evil they're taking and never seem to realize that they can't take the "good" parts out of the deal without acquiring the negative as well until it's almost too late. Once they reach that point, they're almost guaranteed to try to "quit" their newfound lease on life to ensure that it doesn't destroy them and those around them completely. Sometimes they succeed, sometimes they end up dying and regretting having ever started in the first place.

When it's well-executed, this trope can go a long way toward taking the romance out of evil and making it more frightening and personal. When it's done badly, it's a heavy-handed Aesop on the dangers of giving in to temptation and getting involved in something you really shouldn't have.

The trope's name comes from an infamous anti-drug Public Service Announcement from the Partnership to End Addiction, which bore the slogan "This^note an egg on a frying pan is your brain on drugs".

Contrast Evil Is Cool and Evil Feels Good and Good Feels Good. Compare The Dark Side and Evil Is Not a Toy. Also see Drunk on the Dark Side.

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Examples:

Anime & Manga

• Ryo/Kaiser in Yu-Gi-Oh! GX started coming down with life-threatening heart problems after his Freak Out and Face–Heel Turn. At first, it was assumed that it was because of the electroshock collars he became addicted to during his tour through the Underground Duels, but later it was revealed to be a result of the dark power of his own "Underworld Deck", which he forcefully acquired from his old mentor and relied on for most of his villainous career.
• In the Chaos;Head remake's route for Kozue, the lead female winds up pulling this and Evil Feels Good simultaneously. Naturally, it gets worse.
• If you think that Light Yagami is capable of maintaining his sanity after he starts writing names in the Death Note...are you sure you're not evil?
  • Pretty much applies to any Kira, in particular Higuchi, Mikami and (in the films) Takada.
• The Giant Sakura Tree in Da Capo essentially does this to Sakura by granting her subconscious desires even when she begs it not to.
• Most characters in Soul Eater who go through a Face–Heel Turn starts to suffer from quick deterioration of their mental faculties soon after, which is not at all surprising, considering that a Face–Heel Turn in this series usually means giving in to madness. Examples include Franken Stein in the anime; Justin Law and Crona in the manga; and, obviously, Kishin Asura in both.
• Ga-Rei -Zero-: Alas, poor Yomi. She would rather not hurt her little sister (girlfriend?) Kagura, but the evil stone in her head says otherwise. And she realize what is happening to her. And it's far too late for her to turn back.
• Sicks of Majin Tantei Nougami Neuro is so evil that he can simply walk by people and cause them to bend completely to his will, even if they really don't want to. He's a habit that people can't quit.
• The boy who would become Wrath in Fullmetal Alchemist (2003) was a sweet, shy, and innocent young child who was suffering from a nasty case of amnesia when he was first introduced to the audience. Then Envy has him eat unfinished Philosopher's Stones...

Comic Books

• Spider-Man: During the Alien Costume Story Arc, Spider-Man becomes addicted to the power and freedom the Venom symbiote gave him... until he learned that it exacerbated his aggressive tendencies and would've absorbed him into itself in the long run. Peter Parker managed to "quit" the symbiote, but his successor, Eddie Brock, wasn't so lucky. Note that this wasn't actually a part of the original comic book version, but has appeared in all the adaptations. Brock seems to be better, now. At the moment. Sort of. Meanwhile, under the symbiote's influence, Mac Gargan has crawled up the food chain of evil, in more ways than one. A few hosts later, Eddie is currently reunited with Venom, although over the years the symbiote stopped being a bad influence and became much more benevolent.
• Sonic the Hedgehog (Archie Comics) delved a little into this with the Chaos Emeralds. Knuckles' ancestor Dimitri, who would later become the power-mad Enerjak, got hit with the "withdrawal" symptoms of this trope once his Enerjak powers were removed; rendered unchanged by his powers for centuries, their sudden absence quickly reduced him to a frail old man on the verge of death, forced to live on cybernetic means for the rest of his life (and in one possible future, being reduced to a head in a jar).
  • Similarly, in a (now non-Canon) future, Knuckles gets juiced up on Chaos power and goes mad, attempting to reshape his world as he sees fit. He was stopped by Sonic and an alien device, but it robbed him of an eye and all but irreversibly annihilated his relationship with the hedgehog. Note that canonically, he's already been pumped up with Chaos energy once, and while he didn't go insane or anything, he still died (he got better, though). This actually sort of happened in one arc with Knuckles being taken over by the Enerjak power - however, it ended on a better note with Sonic forgiving him, though Knuckles still feels bad about it.
  • Some incarnations of Super Sonic are treated this way, with Sonic usually trying to find a way to subdue his Superpowered Evil Side.
• In the Emerald Twilight arc of Green Lantern, Hal Jordan starts out slightly unbalanced with grief over the freaking demolition of his home city and after a minor nervous breakdown, charges out towards Oa to call out the guardians for their long-running history of being selfish assholes. However, he then starts robbing and killing all the other Lanterns who get in his way, and goes from "unbalanced" to "totally batshit insane" over the space of 22 pages. At the time of publication, it was more a Despair Event Horizon, but it was then retconned that Hal had actually been infected by a fear-feeding Giant Space Flea from Nowhere, meaning Hal apparently lost his mind as soon as he got corrupted.
• 52 established that selling one's soul is not only addictive, but exponentially detrimental to it, lessening its "value" with each trade. This is why a strung-out and desperate Felix Faust tried (unsuccessfully) to barter Ralph Dibny's soul instead.

Fanfictions

• Child of the Storm explicitly has this as a side effect of Black Magic, as in the Dresden Files, with Harry commenting in the sequel that it doesn't take long for someone to go from 'best intentions' to 'Jack the Ripper'. The Arc Villain he's discussing is a case study in this, with his journal excerpts demonstrating his Sanity Slippage to someone who knows what state he's in and doesn't care (in fact, he thinks the addictive aspects are an advantage, as they make him reach further).
• RainbowDoubleDash's Lunaverse: Dark magic works like this, as shown in The Hero of Oaton. Tarnished Copper Coin, feeling down after getting "dumped" by Cheerilee becoming a teacher, winds up living in an abandoned shrine to Tirek. Eventually, the shrine reacts, driving the already not-right-in-the-head young mare to full blown psychosis. By the time Tarnished realises what's going on, the magic's at the steering wheel. Fortunately, Tarnished is able to overcome the magic's control.
• In Departure From The Diary, dark magic is literally addicting, with Tamelyn Riddle declaring that said addiction is the only reason why anyone would use the Unforgiveables, stating that casting the killing curse "feels like a corpse passed through your soul" and is utterly revolting.
• Your Alicorn Is in Another Castle gives Bowser an extra-nasty version of this, in that he didn't even have to make the choice in the first place. He simply was given (or acquired, or something) the destined role of Princess Kidnapper, and when he quite naturally refused to kidnap Princesses he was plagued with intrusive thoughts and other withdrawal-esque symptoms.

Films — Animated

• Pleasure Island in the Disney Animated Canon version of Pinocchio, where bad boys are invited to do what bad boys love to do... until they learn too late it's a trap, and the island is magically imbued to turn them all into donkeys after a while; after they have thus literally made jackasses of themselves, they are sold into slavery. Fortunately for the titular character, he and Jiminy Cricket manage to escape before the transformation fully sets in. The same cannot be said for anyone else, and Pinocchio was likely the only boy to have ever escaped the Coachman's machinations.
• Finding Nemo features sharks trying to give up eating other fish in a Monsters Anonymous setting. When Bruce the shark goes into a feeding frenzy after smelling blood, the other sharks describe it as falling Off the Wagon.

Films — Live-Action

• The Dark Side in Star Wars tends toward the physical aspects of this, slowly twisting, corrupting, and generally uglifying its adherents. In Legends, it's explained that Emperor Palpatine had to leapfrog from clone body to clone body as he grew more powerful, with each one disintegrating faster.
  • From Legends, the ultimate example. Jacen Solo: most talented Jedi of his generation, both in power and in philosophy, able to go past dark and light and see the true Unifying Force behind it. Darth Caedus: all the power of Jacen Solo, half the intelligence, and twice the paranoia. "His cape had betrayed him." Any questions?
  • In the Knights of the Old Republic series, being fully on the dark side causes Glowing Eyes of Doom, wrinkled skin, a change in underwear (to a black-and-red jumpsuit-like thing) and some NPCs comment briefly on your appearance. Although if you were on the dark side and they commented on your appearance, the rest of their lives were generally very brief. A computer in the first game reveals that using the Dark Side actually changes a person's neurological patterns, much like prolonged drug use.
• In Spider-Man 2, Otto Octavius has an epiphany after getting knocked around by Peter, realizing that his arms have been manipulating him, and urging him to evil. Sadly, he was surgically fused with them and may have "died" because Redemption Equals Death.
• In Spider-Man 3, the Venom symbiote has this effect on its hosts, enhancing their physical abilities and increasing their aggression to the point that they stop restraining their darker impulses. Peter is eventually able to fight off its influence after he has an epiphany on what it's turning him into, while Eddie Brock decides that he likes being evil. He becomes so addicted to the power the symbiote granted him, in fact, that he dies while trying to save it from being destroyed by Peter.
• In Mr. Brooks, the eponymous Serial Killer uses Alcoholics Anonymous mantras to try to resist the urge to murder. It doesn't work.
• Loki announces his arrival in The Avengers (2012) by wreaking some serious havoc throughout the rest of the movie, signifying a dramatic change from his previous appearance in Thor. But his mental change for the worse is accompanied by physical changes as well: his hair is even more stringy and mussed than usual, his skin is unnaturally pale, and his eyes are sunken to the point of appearing bruised.
• Karen, the Amoral Attorney and central villain in Michael Clayton. While technically the central antagonist, she turns out to be "merely" a Punch-Clock Villain whose Corrupt Corporate Executive work is visibly shown to be making her extremely edgy and neurotic off the clock.
• In Descendants 3, Princess Audrey steals the staff of Maleficent and becomes a villain, launching a reign of terror on Auradon as the self-proclaimed "queen of mean". During the final battle, she is knocked unconscious, and when she wakes up, she is horrified by her actions, having been freed from the staff's corruption.
• Pulp Fiction opens with this discussion of armed robbery between Ringo "Pumpkin" (Tim Roth) and Yolanda "Honey Bunny" (Amanda Plummer):
  Pumpkin: Forget it, it's too risky. I'm through doing that shit.
  Honey Bunny: You always say that, the same thing every time. "I'm through, never again, too dangerous."
  Pumpkin: I know that's what I always say. I'm always right too.
  Honey Bunny: But you forget about it in a day or two.
  Pumpkin: Yeah, well the days of me forgetting are over, and the days of me remembering have just begun.

Literature

• The Lord of the Rings: Witness what hundreds of years of Ring-addiction did to Gollum, not to mention the Ringwraiths. However, Gollum's appearance may not be so much an example of what happens when you abuse evil, so much as what happens when you live for 500 years without eternal youth.
• The Chronicles of Narnia:
  • The Turkish delight the White Witch gives Edmund in The Lion, the Witch, and the Wardrobe works a lot like a drug — the post-self-isolation, his siblings noting he doesn't look well, "the more he ate, the more he wanted to eat... and if allowed, would go on eating it till he killed himself." Edmund's (music-inspired-by soundtrack only) Villain Song from the 2005 film agrees with this interpretation, with such lyrics as "a life of treats might do me in/but I've got to get another taste" playing up the addiction/withdrawal parallels.
  • In the movie version of The Voyage of the Dawn Treader, the green mist makes Edmund act like a villain again, when he discovers the magic pond that turns everything into gold. He actually wants to convince Lucy into becoming powerful and rich alongside him and tries to get rid of Caspian when he opposes his plan.
• In the Shannara series, if not subverted, at least subdued, in the form of the druid Allanon (as well as his mentor Bremen, and successor Walker) who dared to use the Black Magic out of necessity. Villains used the same power, and it corrupted them. It corrupted Brin Ohmsford, too, until her brother saved her. The druids are different, though; they understand the Black Magic well enough to take this threat seriously, and use it with steadfast discipline and carefully prepared Heroic Willpower strong enough to remain good guys (at least insofar as they do what must be done to vanquish evil) throughout their stint of public service.
• Guards! Guards!: Summoning a dragon from an unknowable dimension and guiding it around the city according to your will? Fun. Addictive, even. Said dragon learning to summon itself into your city and taking its revenge first and foremost on you - your mind, your consciousness, your future? Not fun. Sorry, Mr. Wonse...
• The Dresden Files has Black Magic. When using an evil magic belt in Fool Moon Harry notes that the effect is an amazing high along with the designed effect.
  • The White Council views all Black Magic this way as well and they have a strict policy on what to do with its users.
  • It turns out that the Laws of Magic ("Black magic" being any spell that violates these laws, and warlocks being anyone who uses them) exist because certain spells really do have this corrupting influence on the user, hard enough to resist that no matter the warlock's initial intentions, letting the warlock live typically ended in a high body count.
• The addiction metaphor is pretty obvious in The Strange Case of Dr. Jekyll and Mr. Hyde. The physical symptoms aside, Jekyll even says he can be rid of Hyde any time he wants... but, of course, once he wants to get rid of Hyde once and for all, he can't. The more he takes the potion, the easier (and less painful) it is to transform into Hyde until it's impossible for him to remain as Jekyll. (Note that it is not the potion that is addictive but the freedom from all conscience and moral restraint.)
• In Paradise Lost, although the Forbidden Fruit is not addictive, it does make you feel happy, invincible, and horny, and it also leaves you with a What Have I Done hangover the next morning.
• In the Dungeons & Dragons: Abyssal Plague novels, Kri, after being influenced by Tharizdun.
• Nicolae Carpathia is made of this trope.
• The Haunted Mask of the Goosebumps books invokes this trope, as it slowly corrupts whoever wears it. Carly-Beth Caldwell almost lost her humanity when she attempted to use this mask in a revenge plot. The only thing that can remove the mask is a symbol of love, which turns out to be the only thing that saves Carly-Beth.
• In Harry Harrison's first The Stainless Steel Rat book, the newly-minted special investigator Jim diGriz is faced with the question of locating beautiful psychopath Angelina. He is inspired to synthesise a cocktail of drugs that, to all intents and purposes, turn him into a conscienceless, unempathic, sociopath. In this frame of mind he despises the wimp he used to be, who drew the line at unnecessary violence and murder. The new diGriz delights in inflicting sadistic pain and relishes his chemically adjusted brain's capacity for evil. However, when in the process of tooling up with lethal weapons, he remembers his previous self has booby-trapped the guns just in case. He activates a stun-gas grenade, waking up several hours later with the drug out of his system, having had an insight into an evil mind.
• In The Reckoners Trilogy, using any superpower almost instantly turns you into a sociopath.

Live-Action TV

• Buffy the Vampire Slayer went full-out with the drug comparison when Willow slowly gets addicted to magic. She has to get pulled back from the edge a few times before it sticks, and in the meantime she's a wired sorceress with eyes dilated to the extreme. More tamely, when Buffy gets enticed by the sheer fun of Faith's delinquent and irresponsible behavior, she winds up becoming idiotic enough to burgle a gun shop without any precautions whatsoever, and gets arrested.
• The Dresden Files TV show, being based on the book series, has this. In one episode in particular, it shows the effects on three college students as they "rot from the inside."
• The Apple of Discord has this effect in The Librarians 2014. Anyone who touches it becomes the worst version of themself, with Cassandra Cillian in particular becoming rather murderous. Ezekiel Jones is the only person immune to its effects, as he is already the worst possible version of himself.
• The Dukes of Hazzard: In the Season 7 episode "Dr. Jekyll and Mr. Duke", Luke drinks tainted water (a personality-altering drug) and becomes abusive to his family and conspires — with a band of bank robbers — to rob Hazzard Bank. This leaves Bo, Daisy and Uncle Jesse racing against time to press for answers and stop Luke from making the biggest mistake of his life.
• Highlander had Duncan suffer from a Dark Quickening, which turned him evil ("Something Wicked" S413). He got better ("Deliverance" S414).
• Stargate SG-1's Goa'uld tend to suffer from an actual physical addiction with evil as the primary side effect: the sarcophagus, particularly demonstrated in Daniel's experience with it in "Need". The Tok'ra, an offshoot of the Goa'uld, refuse to make use of the sarcophagus no matter what. They believe it's a major reason why the Goa'uld are Always Chaotic Evil, and consider their own reduced lifespans to be a perfectly acceptable trade-off.
• Sylar from Heroes. Especially in Season 4. It looks like he wants it to stick this time (last time, he gave up because Ma Petrelli's urging of his reform was based on a lie).
• Season 4 of Supernatural has Sam becoming addicted to demon blood to stop the Apocalypse; he knows he's damning himself, but doesn't expect to survive stopping the Apocalypse anyway. Sam Lampshades it: "So you're trying to treat this like some drug intervention?"
• In Once Upon a Time, Rumplestiltskin becomes increasingly violent and paranoid to the point of even killing his mute servant who had a drawing of the dagger, after becoming The Dark One. He is shown to be extremely unhinged throughout the series.

Tabletop Games

• Chaos tends to do this in Warhammer and Warhammer 40,000. Its effects are best summed up in five words, usually shouted: "SANITY IS FOR THE WEAK!"
  • Of course backing out really isn't an option once you start worshipping Chaos. Not only have you made deals with extradimensional daemonic entities for your powers (and yes, they WILL come and collect), once you have been associated with Chaos (or knew someone vaguely associated with chaos, or lived in the same village as someone associated with Chaos) then chances are the good guys (such as they are) will also be trying to kill you. And no, "I've quit" will not be taken as an excuse.
  • God help you if you worship Tzeentch, Khorne, or Slaanesh. Actually, God can't help you, because they ARE your god.
    • Khorne, being the god of slaughter and bloodlust, will turn you into a battle-hungry psychopath one way or another, whether you want to or not (and by that time you probably do).
    • Tzeentch, the god of Just as Planned and Sorcery, will grant you uncontrollabe telepathy, constant whispering always in your head, and can make you SEE FOREVER. Few people remain sane.
    • And finally Slaanesh, god of pleasure and excess; by the time he / she / it is done with you, your senses will be so dulled and jaded that you will need to censored at least three times over to even chuckle.
  • Pft, what about Nurgle? He's probably the nicest, friendliest god in all of Warhammer (yes, even nicer than the "good ones"). Heck, all he wants to do is give you a hug and some gifts, and his worshipers even call him Papa! Of course his "gifts" are plagues so virulent that a single microbe can infect an entire world within a few days, cause your guts to bloat until they burst and you're dragging around your own intestines, infest you with hundreds of horribly pestilent insects, and may even turn you into a literal zombie. Before all of that, of course, you've gone so insane from the constant pain and suffering that when Nurgle says he'll relieve you of it if you worship him you happily take it up; he doesn't actually make you better though, he just makes you enjoy it, and now you want to share Papa Nurgle's gifts with everyone else..
    • By which point you've become ridiculously tough and more or less immortal and immune to pain, moreso than other Chaos mutants, so if you don't want to be pretty or fast (though the latter isn't necessarily ruled out), Nurgle's gifts are the genuine article... usually^note There are Nurgle zombies, which are mindless, but these seem to come about when Papa or more commonly one of his faithful is attacking enemies or innocents without the goal of empowering anyone or securing worshippers, and there are the usual risks of becoming a Chaos Spawn or just snapping under the pain and becoming ineffective before you learn to live(?) with it. And you still get to have a decent social support network (for a strictly quality-oriented definition of "decent"), something the other 3 Ruinous Powers don't offer. All of this is not to say that Nurgle averts this trope, but he seems to be the best Chaos has to offer in Warhammer 40,000 by a considerable margin.
    • With Tzeentch, he also gives you shapeshifting, and does seem to care about his worshippers to some extent, he even intervened to save the Imperium during the Horus Heresy! Really, Tzeentch is unknowable. Nothing you can say about him is known for sure, and his followers seem less likely to commit travesties than other Chaos Gods.
• Vampire: The Requiem has this as the weakness of the Ventrue clan. Every character, once they fall down the Karma Meter, needs to roll to see if they pick up a Derangement as part of sublimating the fact that they did something awful. Ventrue get a penalty to this roll, making them more likely to pick up Derangements as they do bad things.
• The Inspired are all mad scientists to begin with, but if they fall down the Karma Meter, the 'mad' part becomes ever more prominent. Grimms become irrationally angry, Hoffnungs tend to turn narcissistic, Klagen get depressed, Neids become paranoid, and Staunen lose their focus on the mundane world. Drop all the way down (or push yourself way too far), and the madness completely overwhelms your personality, turning you into an Illuminated.
• Princess: The Hopeful: Among other effects, becoming Darkened inverts the effects of Virtue and Vice (making Virtues less emotionally fulfilling and Vices more), and gives a -2 penalty to future Breaking Point rolls. Also, several Umbrae have unpleasant mental side effects, such as the perpetual stress and inability to relax that comes with the Cruel Confidence Umbrum, or the paranoia of the Skittering Spider's Sense Umbrum.
• Dungeons & Dragons has the Helm of Opposite Alignment, a cursed artifact that forcibly reverses the alignment of any weak-willed character who puts it on, and states that "The individual changed by the magic thoroughly enjoys his new outlook." A normal-looking helmet that turns you evil and makes you LIKE IT, violently resisting any attempt to change back. (assuming you were good to begin with, otherwise this could just as easily be a case of forced Good Feels Good via a little...magic)
• Demon: The Fallen has Torment, the stat that reflects all the baggage the Fallen carry after having spent millennia in the Abyss. Demons can work it off so that they can become the angels they once were... however, willingly taking on Torment allows the demons to apply new applications of their Lores and unlock new powers in their apocalyptic forms, so some of the more bloodthirsty Fallen may wonder what's the point of healing your pain anyway...

Theatre

• Christopher Marlowe's version of Mephistopheles (in Doctor Faustus):
  Why this is hell, nor am I out of it. Think'st thou that I, who saw the face of God and tasted the eternal joy of heaven, am not tormented with ten thousand hells in being deprived of everlasting bliss?

Video Games

• In Fable, indulging in evil acts eventually mutates your form into a smoking, horned, flies-buzzing-around-you Palpatine wanna-be, who frightens nearby villagers just by the mere sight of you. Like your other actions in the game, though, this is only a superficial change, and doesn't do anything to change the story or your character in any significant way.
  • Fable II introduces corruption and purity in addition to good and evil. As a result, it's possible to be pure evil, which results in a pale-skinned, Glowing Eyes of Doom appearance, or corrupt evil, which results in a demonic form, complete with horns and fissures of evil. However, despite your appearance, it's possible to be a Villain with Good Publicity if you play your cards right, and people will just LOVE that random demon walking through town.
• The Dark Prince in Prince of Persia: The Two Thrones mates this with Superpowered Evil Side; at first, the Prince sees the Dark Prince as an asset, but once he realizes the evil selfishness it embodies, he refuses to even listen to it (and you're unable in-game to switch to him after this point) until you fight him in the final battle. Also, when the Prince changes into his dark persona, he loses health rapidly, necessitating the need to get rid of it.
• In Baten Kaitos: Eternal Wings and the Lost Ocean, the main character Kalas betrays the party and becomes completely corrupted by the power of a dark god until he consciously chooses to reject it.
• Iori (and Leona's) transformation into the Riot of the Blood state in The King of Fighters is preceded by dizziness, hazy vision (as they lose their consciousness), and finally, vomiting up blood. Unlike many other examples here, this is completely involuntary (they have Orochi's bloodline within them, which means those with a close enough connection to Orochi or Orochi himself can cause them to descend into this state forcibly).
• Riku in Kingdom Hearts (and, to a lesser extent, anyone who uses the darkness for a quick and easy power boost).
• In Mega Man Battle Network, many Navis initially use dark chips to become more powerful, but soon become addicted to them and start suffering withdrawal without them.
  • This is shown in game as the use of a dark chip deducts one point from your maximum HP...permanently. Deep in the Undernet you bump into navi-shaped shadow viruses stated to be the ultimate result of a navi completely giving in to their addiction.
• Kefka in Final Fantasy VI. He was once a perfectly normal Imperial General, until he got his magitek infusion. The process was still experimental and eventually drove him so far off the deep end he became the first Final Fantasy antagonist to successfully unleash the apocalypse before he was killed.
• The Big Bad in Final Fantasy XV suffers from this. Ardyn Lucis Caelum was a wise and noble healer king of Lucis, who absorbed countless daemons into himself to protect his people. This had the small side-effect of driving him insane. Not helping the matter whatsoever, the very gods who gave him that power and the very people he healed betrayed and ostracized him, rather than help him. This resulted in him going completely off the deep-end, embracing both his own insanity and evil nature of the daemons, all so he can eventually exact the perfect revenge. Also, he's one of the few FF antagonists who successfully unleash the apocalypse. The Ardyn DLC reveals that the Starscourge itself didn't turn him evil. If anything, the demons strengthened his sanity. Rather, the insanity came from devouring the minds of his human victims and that of a god. Which makes sense since the Starscourge isn't actually a magical evil plague — it's "just" a horrifically mutated virulent strain of malaria.
• Mass Effect 2 has This Is Your Face On Evil; choosing a lot of renegade actions will cause Shepard's facial scars to become more visible and horrific-looking. A Shepard who does enough renegade actions will eventually have glowing red eyes. It's given a Hand Wave with the notion that a more positive and altruistic outlook (ie, playing Paragon) helps the scars heal, but a more aggressive and violent disposition (Renegade) make it harder for them to fade, and in fact worsens them.
• In AI: The Somnium Files, Big Bad Saito Sejima was born with a brain defect that made him unable to produce oxytocin (the hormone associated with love and pleasure) except when killing. This is what made him become a Serial Killer, as it was the only way he could feel any positive emotions. Due to Body Surfing shenanigans, Saito ends up in a body that does secrete healthy amounts of oxytocin, but at this point he's addicted to the stronger rush his original brain gave him from killing, and only wants to return to his own body so he can continue killing for fun. Meanwhile, the one who ended up in Saito's body is prevented from becoming Ax-Crazy thanks to synthetic oxycotin (which tragically proves that Saito's condition could have been treated if he had received proper care).

Webcomics

• Parodied in this The Thrilling Adventures of Lovelace and Babbage (aka 2D Goggles) strip, given that for Ada, Poetry -> Evil.

Web Original

• Post Face–Heel Turn Madison Conner of Survival of the Fittest going from a (very) emotional girl just trying to survive and transforming into a sadistic psychopath with little to no empathy. There wasn't even a trace of Character Development, making it incredibly jarring.

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Parents, talk to your children about using evil. They'll listen...