History Characters / MegaManXSigma

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[[center:[[WMG: [-'''''VideoGame/MegaManX ''''' | [[Characters/MegaManX Main Character Index]]\\
[[Characters/MegaManXHeroes Heroes]] ([[Characters/MegaManXX X]] | [[Characters/MegaManXZero Zero]]) | [[Characters/MegaManXVillains Villains]] ('''Sigma''' | [[Characters/MegaManClassicDrAlbertWWily True mastermind]]) | [[Characters/MegaManXMaverickBosses Maverick Bosses]] | [[Characters/MegaManXSupportingCast Supporting Cast]]]]]]-]
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!!Sigma
!!!'''Voiced by''': Creator/{{Mugihito}} (JP), Charlie Fontana (EN, ''X4''), Walter Roberts (EN, ''X7''), Dave Petit (EN, ''X8''), Gerald Matthews (EN, ''Maverick Hunter X''), Chandler Van Fossen (EN, ''X4'' redub), Jim Byrnes (EN, animated series), Creator/ChrisTergliafera (EN, ''VideoGame/MarvelVsCapcomInfinite'')
[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/megamanxdive_sigma.png]]
[[caption-width-right:350:From ''VideoGame/MegaManXDive''.]]


The [[BigBad primary antagonist]] of the ''X'' series. One of the most advanced and powerful Reploids ever made, he was the greatest creation of Dr. Cain. When the Maverick Hunters were formed, he was chosen to be their leader and uphold peace around the world, leading them to many victories and successes. One fateful day, however, following an encounter with the recently-unearthed Zero, he was exposed to the Maverick Virus, a virus that changed the thought processes of a Reploid and usually made them unruly and violent.

Instead of simply being infected, however, Sigma's advanced nature caused him to became one with the virus, and the process turned him into a murderously insane maniac bent on ending the human race. He's appeared in many bodies throughout the series, and Sigma is never usually the same each time. No matter what form he takes, however, one thing is always consistent: as long as the Sigma Virus lives on, Sigma lives on.

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* AmbiguousStartOfDarkness: From the first game's manual, it was always established that he led his Maverick rebellion as he believed that humans were limiting the evolution of Reploids. However, later games would establish that Sigma went Maverick after his fateful encounter with Zero, which would get the former infected with the Maverick Virus to merge with Sigma's mind to form the Sigma Virus. It is therefore unclear whether Sigma turned evil entirely because of the virus messing with his mind or Sigma was always resentful of humans with the virus merely giving him the means to carry out his rebellion. However, some of his characterizations pre-virus (in the X4 flashback and an archive of his old data on Dive) showcase him to be fairly reasonable.
* ANaziByAnyOtherName: For the first few games, his attitude about humans can be summarized as "the inferior need to be exterminated so the superior can thrive". He then extends this attitude towards earlier reploid models for the sake of the Next Generation ones.
* AnimalMotifs: Wolves. He has a pet robot wolf named Velguarder, his OneWingedAngel form in the first game is a large robotic wolf, and his symbol is the Greek letter Sigma designed as a wolf.
* AnthropomorphicPersonification: He's the living will of the Sigma Virus - it's even named after him. It's heavily implied that [[AsLongAsThereIsEvil as long as the Sigma Virus exists there's always a chance that he could return.]]
* ArchEnemy: To both protagonists X and Zero.
** Sigma is greatly interested in X's potential and wants to use his body to usher in a new age of Reploid supremacy. Sigma even comments on how he and X are "always destined to meet".
** Zero is the one who infected Sigma with the virus in the first place, and [[TheAtoner is greatly disturbed by what he did to the former Maverick Hunter]]. On Sigma's end, he indirectly causes [[spoiler:Iris' death]], even [[KickTheDog mocking Zero about it]], and later goes along with Dr. Wily's posthumous plan to turn Zero into the monster he was meant to be.
* ArcWelding: His evolution talk calls to mind later {{Big Bad}}s [[Videogame/MegaManZX Serpent]] and [[spoiler:Lumine]]. It's not clear where Inafune was going with this, as the remake series was canceled.
* ArcWords: "Evolution requires sacrifice."
* ArtificialZombie: In ''X6'', he is brought back into a half-dead state by Gate.
* AsLongAsThereIsEvil: Tells X this when defeated in ''Xtreme'', promising to haunt him and Zero for as long as they live.
* AttackItsWeakPoint: Most of the time, his second body's weak point is located on the head.
* AsskickingLeadsToLeadership: Dr. Cain built Sigma to be the leader of the Maverick Hunters and consequently to have the power to match the post. At the time of his creation, Sigma was ''the'' most advanced Reploid in the world both on a physical level and with the most advanced anti-virus software installed that would, in theory, prevent him from going Maverick and thus turning that power against humanity. He continues to hold true with this more or less as the leader of the Mavericks.
* AxCrazy: His sanity seems to wane as the games go on, where he becomes less concerned with helping Reploids advance in their development and far more obsessed with killing the heroes while wiping out millions of innocent lives in the process. And in the reboot of the first game, he already shows signs of this, such as laughing maniacally while looking down at the ruins of a city he obliterated via missile launches.
* BackFromTheDead: Again and again and again and again... at last count, he's been killed ten times. In the strictest sense, the only times where it seemed like his death might stick were in ''X3'', where he's first hit by a real anti-virus, ''X5'', where Zero destroys him after most of the Sigma Virus has been eradicated from the Earth, and ''X8'', where he is [[spoiler:destroyed on the moon, [[KilledOffForReal and hasn't been seen since]]]].
* BadassBoast: He loves giving these out. Not just prefight ones, but even after he has seemingly been defeated, most notably as TheStinger for the first game.
* BadassCape: A staple of Sigma's. Most notable in his ''X1'' and ''X5'' forms, but in ''X4'' he wore a Grim Reaper cloak and in ''X2'' he only wore a cape in artwork. Subverted with his tattered robes in ''X6'' and ''X7'', which serves to make him look beaten and haggard rather than intimidating.
* BadBoss: In the non-canon Vile Mode of ''Maverick Hunter X'', he allows Vile to kill a ton of his Mavericks, including his high-ranking generals, to test Vile's potential.
* TheBadGuyWins: Sigma's actions in [[spoiler: ''X8'' ensure that new generation Reploids will continue to go Maverick for eternity despite their viral immunity, effectively ensuring that his legacy will live on no matter what]]. Only in the ''Zero'' series does his plot finally crumble. He also defeats both X and Zero in ''The Day of Sigma'', successfully launching a missile strike.
* BaldOfEvil: He is built to be bald, unlike many other robots, and is a terrible Reploid, although he was once the heroic leader of the Maverick Hunters.
* BatmanGambit: In ''X4'' and ''X5'', his plans rely on the personalities of General, [[HonorBeforeReason Colonel]], X, Zero, and Maverick Hunter policy. This is turned way up in the manga rendition of ''X4'', where he relies on the Repliforce Coup (and was the setup of it thanks to Double), wherein all the Repliforcers are absolutely crazy (like the necromantic Web Spider or the "I'm going to [[BadBoss kill my own troops]] and drive a super train through a populated city" Slash Beast).
* BatterUp: His "[[JapaneseDelinquents Gangsta]]" variant in ''X [=DiVE=]'' has a baseball bat as his default weapon.
* {{BFG}}: In ''X7'', one of his attacks has him pull out one of these.
* {{BFS}}: Special mention to ''X8''[='s=] BFS, the aptly-named "Σ Blade" which in addition to length is probably the widest and thickest sword he's ever used as well. The animated opening to ''X3'' depicts the first game's saber as a BFS.
* BigBad: Of the entire series as a whole and of nearly every individual game, with the exceptions of ''X6'' (where Gate is the main villain and uses Sigma as a GodzillaThreshold), and [[spoiler: ''X8'' (where Lumine takes advantage of Sigma for his own plans)]].
* BigNo: Lets one out after his defeat in ''X8''.
* BreathWeapon: In ''Maverick Hunter X'', Sigma's wolf form can breath fire from its mouth. In ''X5'' and ''X6'', Sigma can fire lasers from his mouth.
* BroughtToYouByTheLetterS: All the Mavericks directly under Sigma would have his [[GratuitousGreek symbol]] somewhere on their person.
* CameBackStrong: In ''X5''. After getting inflicted with Doppler's antivirus in ''X3'', and getting destroyed again in ''X4'', Sigma is back yet again, and has not only completely overcome the effects of the antivirus, but is even more powerful than ever. He can bind himself directly to machinery and transform it to his will, and trying to destroy him again only allows the Sigma Virus to spread across the entire planet!
* CameBackWrong:
** [[spoiler:Gate revived Sigma. Unfortunately, he apparently ruined his sanity in the process.]] He gets better by ''X7'', though. Curiously, when seen holding conversations with Red as "The Professor" and during the ending of ''X7'', Sigma appears in a state of disrepair not unlike [[spoiler:in the sixth game]]. This suggests that, between spreading himself too thin across the globe during the Earth Crisis and his botched resurrection only a few weeks later, while Sigma's mind eventually recovered, the damage to his body and programming/viral coding may have been permanent, perhaps leading to his ultimate defeat in the following installment.
** It's implied that this first happened earlier, just after ''X3''. At first, Sigma could manifest in his viral form and attempted to possess X to finally defeat him, only to be struck with Doppler's anti-virus. While his return can be explained by [[VideoGame/MegaManXtreme2 Berkana's]] experiments, he never again tries to possess X or assumes his viral form again, and instead shifts his focus to Zero.
* CanineCompanion: Velguarder. He sics him on you before fighting you himself in the first game.
* ClassicalMovieVampire: He has a Halloween variant in [=DiVE=] whose attire pretty much mirrors the classic {{Dracula}}.
* CloakOfDefense: In the manga adaptation of''X1'', Sigma's cape is able to protect him from enemy attacks. This becomes essential to X surviving the destruction of Sigma's fortress when he uses the discarded cape to protect himself during the descent.
* CloneAngst: In the ''X1'' novelization, Sigma has a freakout when he discovers that he and all other reploids were made from X's designs making them "flawed copies." This of course leads to his rebellion.
* TheCoatsAreOff: He throws away a cloak before fighting you in ''X1'', ''X4'' (after X/Zero burned it off), and ''X5''.
* ContinuityNod: His OneWingedAngel from ''X5'' is Gamma, the FinalBoss from ''VideoGame/MegaMan3''. And it was given to him by [[spoiler:Dr. Wily]].
* CreateYourOwnVillain: In a meta-sense. Sigma claimed humanity and the Maverick Hunters would turn on Reploidkind if they stepped out of line, thus necessitating their destruction. His and his successors' many years of attempted genocides and near-apocalypses would go on to create [[VideoGame/MegaManZero Dr. Weil]].
* DeathOfPersonality: Neither X nor Zero ever were made aware, but X4 and WordOfGod clued in the audience that the "Sigma" who incites war throughout the series isn't even the genuine article. Commander Sigma, the Maverick Hunter, ceased to be when he first encountered Zero, ''long'' before the series ''even started.'' [[DeathOfPersonality His consciousness was overtaken and assimilated by the Maverick Virus]], causing it to mutate into the Sigma Virus, which walked around in his body until X first destroyed him.
* DeaderThanDead: In ''X8'', as he died [[spoiler:on the moon.]] This is somewhat confirmed with his absence in ''Command Mission'' (set in 22XX). Coupled with the events of ''X4''-''X7'', it is speculated that the Virus may have lost much of its potency [[spoiler:on the moon]], judging by Sigma's unfinished true body and Lumine's remarks after Sigma is defeated. Even then, [[spoiler:the presence of his DNA in the copy chips of the New-Gen Reploids (whose production was restarted later on)]] likely provides a backdoor for him to return anyway. However, By the time of ''VideoGame/MegaManZero'', X is said to have used the Mother Elf (a "Sigma Antibody Program" created from the Maverick Virus data in Zero's body) to erase all traces of Sigma's DNA and end the Maverick Wars.
* DegradedBoss: [[spoiler:In the later part of the secret final stage of ''X8'', you can see multiple New Gen Reploids transforming into Sigma to fight you. They all die easily like other mooks (though they're among the harder of mooks), and their attacks aren't as strong as real Sigma's.]]
* DiscOneFinalBoss: [[spoiler:In ''X8'', which served as a MetaTwist since usually Sigma was the one who was [[ManipulativeBastard manipulating the supposed main bad guy]], instead of the main bad guy manipulating Sigma.]]
* DoubleWeapon: In ''X7'' his main weapon is a giant rifle that he can split into two smaller rifles.
* EnemyCivilWar: His ''X4'' plan is to set one of these up. It works perfectly because the Repliforce is [[HonorBeforeReason not very bright]].
* EnergyRingAttack: In his final form, Sigma can fire rows of blue energy rings from his hands.
* {{Engrish}}: Used deliberately in ''X6'' to show how badly deteriorated his mind is after [[spoiler:his imperfect resurrection]].
* EvenEvilHasStandards: In ''Xtreme 2'', a throwaway line in his reveal implies that Berkana's entire "Soul Erasure" plan to feed upon the DNA Souls of Reploids was too far, even for him, and congratulates the Hunters for dealing with her -- though he also promptly comments that the whole affair amused him enough to not intervene until she was dead, so he's still a bastard.
* EvilCostumeSwitch: While a commander in ''The Day of Sigma'' he has a relatively simple green look. After getting his eyes scarred and going Maverick, he adds spikes on his wrists, extends blades from his back, and equips a flowing red cape.
* EvilIsBigger: Regardless of what body he's using, he's always much larger than X and Zero.
* EvilIsNotAToy: [[spoiler:Gate ''admits'' that he's risking his own life bringing Sigma out, but he has no choice at this point with X/Zero having exhausted all other options. Sigma quickly shows Gate he should have taken his chances and blasts the scientist away.]]
%%zce* EvilLaugh: He loves doing this.
* EvilPlan: It's always to destroy the humans, somehow.
* EvilSoundsDeep: Particularly in ''X4'', where his voice sounds similar to a slasher movie villain, in ''X7'', where he sounds like [[WesternAnimation/InspectorGadget Dr. Claw]], and in ''[=MVCI=]'' where he has a voice remarkably similar to [[Manga/JojosBizarreAdventureStardustCrusaders Mohammed Avdol]].
* EvilutionaryBiologist:
** He follows the robotic version of this, especially in ''Maverick Hunter X,'' where he wants to see the true potential in Reploidkind. His plan is to prove this potential by pushing X to his limits.
--->'''Sigma:''' "Evolution requires sacrifice."
** In the aftermath of the X vs. Zero battle in ''X5'' [[spoiler: (should Zero not go Maverick)]], Sigma similarly expresses disappointment that Zero was unable to evolve to his [[SuperpoweredEvilSide "true self."]] Should Zero be brought to the final battle in Zero Space against Sigma, Sigma gives one more try at tempting Zero with the power he'd (re)gain when awakened, but Zero doesn't bite.
* {{Expy}}: Has most of his traits from Char's Counterattack as a Dark Messiah judging humanity by rebelling against them as another race in a much brutal fashion and even his legacy goes on afterwards transcending to another plane of existence and transferring his another kind into another body. He is shown to be {{manipulative|bastard}} to his allies and treats them nothing more but a piece of pawn in his game and develops a rivalry with the blue schemed protagonist throughout the series.
* EyesAreUnbreakable: The attack that gave him his trademark scars did nothing whatsoever to his actual eyes. Subverted when Maverick Zero does, in fact, gouge out one of his eyes along with half of his face, and in ''Maverick Hunter X'' where he, in his OneWingedAngel form, is shown having his right eye missing.
* EyeBeams: In ''X4'' and ''X8''.
* EyeScream: Both Maverick Zero and X have gone for his eyes in the past. The latter inflicted burn scars in the process. Since Sigma's a robot, we are usually spared [[{{Squick}} the worst]] of this trope.
* FaceHeelTurn: Was once [[LawmanGoneBad a member of the Maverick Hunters]] and [[FallenHero a noble Reploid at that]], but then he was infected by Zero's virus and the rest is history.
* FakingTheDead: In ''X5'', he straight up is taken out in the very first boss fight [[ThanatosGambit solely to let his virus spread across the Earth]], forcing the heroes to put any proper searches for him on the backburner to deal with the Space Colony Eurasia. He doesn't actually show up again after that until the endgame in the aftermath of the X versus Zero duel to try to pick them off. However, the duo aren't really surprised at all, given it was obvious that ''something'' of Sigma was buried deep in the ruins with how much concentrated virus was in there, and unlike [[HijackedByGanon most of the rest of the series]] it's explicit that this game was his plot from the start, [[spoiler:his teamwork with Dr. Wily aside.]]
* FallenHero: He wasn't just a random Maverick Hunter who turned to evil: he was their leader and became the biggest threat to the world and the leader of the very enemies he fought in the past.
* FantasticRacism: Once he was infected, his compassion for those who served under him in the Maverick Hunters becomes twisted by the Maverick Virus. Now he believes humans to be inferior to Reploids, and most of his plans through the series involve the slaughtering of the human race.
* FantasticTerrorists: Terrorizes and razes multiple locations to help his cause of overthrowing humanity and achieving his idea of Reploid evolution.
* FatalFlaw: {{Pride}}. His being infected in the first place is partially his fault for screwing around when fighting Maverick Zero in ''X4''. That and he has some ''terrible'' judgment regarding his battle bodies, even if they aren't complete.
* AFatherToHisMen:
** Back when he was still commander of the Maverick Hunters, when they managed to corner the single rogue maverick [[spoiler:(Zero)]], he insisted going in by himself as he couldn't bear the idea of losing more of his men.
** The second and third ''VideoGame/MegaManXDive'' Halloween events (ironically enough) and the Reploid Air Force chapter give a glimpse of what Sigma was like before he was corrupted - a genuinely pleasant and nice guy who was supportive of his comrades and subordinates, and even a bit playful at times, in a good way. Both [=RiCO=] and [=ViA=] can't help but feel a bit of whiplash from meeting the series BigBad from before he became evil. It makes his fall from grace look far, far more tragic in hindsight, especially considering he had no agency in said fall whatsoever from the moment he was infected.
* FauxAffablyEvil: Only in ''X1'', before his decreasing sanity, he acts quite polite to X before their fight, congratulating him for making it this far, yet saying he is ''almost'' as good as he was.
* FightingAShadow: Eradicate his current body, his viral self is still intact. Erase it, and a backup copy will pop up later in a new body. It takes [[spoiler:killing him on the moon]] to finally destroy him, supposedly because his viral form will (presumably) just fade away to nothing with no other robots to infect there.
* FireIceLightning: Sigma's final form in ''X4'' has a move consisting of three robotic heads- one blue, one red and one yellow. The red one attacks with fire, the blue one with ice and the yellow one with lightning.
* FinalBoss: Appears as the final adversary in all games in one form or another [[spoiler:with the exception of ''X8'' and ''Command Mission'', the former where he's the [[DiscOneFinalBoss penultimate boss]] and the latter [[PutOnABus where he's nowhere to be found]]]].
* FlingALightIntoTheFuture: A villainous take on this. [[spoiler:In X8, Sigma seemed to finally acknowledge his increasing decay and limited time, so he hijacked the production of New Generation Reploids to instill his personal data across all of them -- save for Axl, who narrowly avoided the impromptu "adoption". While Sigma's next stand appeared to have finally been his last, it didn't matter, because he effectively created an ''entire line of Sigmas'' to succeed him. Unfortunately for him, all of this effort is eventually undone by the Mother Elf.]]
* {{Foreshadowing}}: Sigma, when trying to recruit General to revolt against humanity, claims that humanity will try to destroy anything that doesn't obey them completely. Come the ''VideoGame/MegaManZero'' series, as well as Weil's BadassBoast in ''Zero 3'', it turns out Sigma was ''right.'' [[SelfFulfillingProphecy Though it may have been due to constant, genocidal Reploid revolutions that he personally helped cause]] which made Weil decide Reploids couldn't be trusted with free will.
* GeniusBruiser: A brilliant tactician and genius, and is more than capable of fighting the heroes with giant, muscular bodies.
* GiantHandsOfDoom: In his second form in ''X1'', ''X5'', and ''X7''.
* GoneHorriblyRight: Sigma was designed with the most advanced anti-virus software at the time of his creation in the hopes he would be able to fight off any infection. When he ''was'' infected by the Maverick Virus [[spoiler:due to his battle with Zero]], his programming did indeed attempt to fight it off by [[FusionDance merging with it]], [[DeathOfPersonality destroying his old personality]] and in the process going from being being infected by the virus to becoming the virus itself.
* GrandTheftMe: Tried to pull this on Red in ''X7'', but failed [[spoiler:due to him being Axl]]. Before that, he also attempted this on X in ''X3'', but [[spoiler:either Zero or Doppler blasted him before he manages to.]]
* GrimReaper: His first form in ''X4'', [[ManipulativeBastard while orchestrating a massive civil war between two armies, and then trying to use a]] KillSat [[OmnicidalManiac to commit genocide]]. He even comes complete with an [[SinisterScythe Laser Scythe!]]
* GunsAkimbo: His primary weapons in ''X7''.
* HijackedByGanon:
** He succeeds Wily in this department. The list of his hijackees include the X-Hunters in ''X2'', Dr. Doppler in ''X3'', the Repliforce in ''X4'' (although this was {{lampshade|Hanging}}d by one of the bosses, and Sigma's involvement is strongly hinted at as early as the cutscene right after the intro stage), [[spoiler:Gate in ''X6'']], and Red Alert in ''X7''. He even pulls this off in both ''Xtreme'' games, controlling Techno and somehow behind Berkana and Gareth between the respective stories. Surprisingly, this doesn't happen in ''X5'' [[spoiler:and ''X8'']]; ''X5'' has Sigma acting out a plan made with a partner who's implied to be [[spoiler:Dr. Wily, and in ''X8'' Sigma is Hijacked by Lumine.]]
** [[spoiler:''X6'' is also an interesting case in that Gate is still the true mastermind of the game, as Sigma's current incarnation is an unstable zombie who was revived simply because Gate thought he needed a backup plan against X and Zero (plus some possible influence from the Maverick/Zero Virus). He just kills Gate after his defeat, and X and Zero go after him because... well, it's Sigma.]] X practically lampshades Sigma's presence [[spoiler:in ''X6'']].
---> '''X''': Sigma... we don't have time to deal with you. We need to rebuild our world and I can't let you get in our way. It doesn't matter how many times you'll come back... I'll beat you!
* HornedHumanoid: Continuing the [[Literature/TheBible Biblical symbolism]] present in ''X8'', [[spoiler:Sigma's true appearance in that game (as opposed to the Copy Sigma fought at the Gateway) is a devil-like figure with slightly distorted facial features, the scraps of metal that constitute his incomplete body seemingly held together only by the Sigma Virus.]]
* HoverBot: Shows up as a huge floating head at the start of ''X5'' as a WarmupBoss.
* HumongousMecha: His ''X5'' and ''X7'' forms are by far the largest bosses in the series.
* {{Hypocrite}}: For all his feigned concern about human oppressors disposing of any reploid that fails to obey them, he was perfectly willing to dispose of every reploid on Earth in order to achieve his goal of exterminating humanity with Final Weapon, as well as his use of threats, reprogramming and viruses to compel reploids to follow him/his way of thinking.
[[/folder]]

[[folder:I-Z]]
* ILetYouWin: In ''X5'', the first boss fight is against Sigma in the form of a large floating head. After the player defeats him, a virus breaks through Earth, which was what he wanted. Zero clearly states "he lost to us on purpose!"
* IllKillYou: [[spoiler:In ''X6'', he's reduced to just wanting to kill the heroes, having his [[SanitySlippage mind deteriorate]]. "[[ItHasOnlyJustBegun THE BADDLE HAZ JUSD BEGUNN!]]" "IWILLSHOWYOUWHATATERRORISALLABOUT!!" "JUSDIE X!!" "[[SayMyName ZELLLLLLO!!!]]"]]
* INeedYouStronger: Why he doesn't up and finish X off at the end of ''The Day of Sigma''. He also spares Zero because [[UnderestimatingBadassery he doesn't know who he is]] or exactly what he is.
* IronicEcho: In the OVA, Sigma tells X that there are times that X should never hesitate to pull the trigger as words of encouragement and also a lecture after an incident where Sigma had to get involved in decommissioning the Maverick due to X hesitating after it used a captured soldier as a Reploid-shield. Sigma later says that exact thing when he is strangling Zero after becoming Maverick to taunt X, and unveiling that he's going to nuke Abel City to the ground as the start of his Reploid rebellion.
* JapaneseDelinquents: His "Gangsta" variant in ''X [=DiVE=]'' dresses up like the typical Japanese school gang leader, complete with a CommissarCap and a [[BatterUp baseball bat]] for a weapon.
* JokerImmunity: Keeps getting killed ([[VideoGame/MegaManX5 sometimes dying twice in a single game]]!), but he just will not die due to his form as a sentient computer virus, and since he's in the future with robots galore, there's no shortage of things to bodysurf into. However, he ''finally'' gets it revoked in ''X8'', where [[spoiler:after getting blown up on the ''Moon'' of all places, he finds that there's nothing left to jump into on its barren surface, and dissipates harmlessly and somewhat anticlimactically.]] Even assuming ''that'' didn't finish the job, the ''Zero'' series reveals the Mother Elf anti-virus program basically eradicated both the Maverick and Sigma Viruses from the world, ensuring that Sigma would never be able to return.
* KickTheDog: Employs a particularly bad verbal one to Zero before their battle in ''X4''. After revealing how he orchestrated the conflict with Repliforce, which led to [[spoiler:[[ILetGwenStacyDie the death of Iris at Zero's hands]]]], Sigma cruelly taunts the emotionally torn-up Hunter with [[spoiler:[[TogetherInDeath "Iris is waiting for you!"]]]]
* KillAllHumans: His goal, in order to lead the way for Reploid evolution.
* KilledOffForReal: Zig-zagged a lot, thanks to his JokerImmunity. In ''X3'' his viral essence was seemingly erased by Doppler's vaccine... only for him to make an UnexplainedRecovery in ''X4''. Then he seems to die for real again in ''X5''... only for Gate to revive him out of desperation. He finally dies for ''real'' in ''X8''. Even after that, the ''VideoGame/MegaManZero'' series reveals that his Sigma Virus lingered on and caused trouble years until the Mother Elf finally finished it off.
* LanternJawOfJustice: Inverted with his massive Chin of Villainy. Played straight in his pre-infection days, where he genuinely was a noble warrior.
* LargeAndInCharge: Even before he goes OneWingedAngel, he's pretty tall and the leader of the Mavericks.
* LargeHam: ''Especially'' at the end of ''The Day of Sigma'' {{OVA}}. He's no slouch in the other games, either. And his hamminess grows as his sanity decays to the point that by the eighth game, he's constantly shouting all his lines.
-->'''Sigma''': "Come and get me X! The time has come to prove your mettle against me. This fight will decide the fate of all Reploids! [[TheWarHasJustBegun The battle may be over, but the war is just beginning]]! [[EvilLaugh MUWAHAHAHAHAHAHAHAHAHAHA!!]]"
* LaserBlade: His weapon of choice in ''X1'' and ''[[{{BFS}} X8]]''.
* LastBreathBullet: In ''X5'', Sigma starts it by shooting X and Zero at the same time with a back attack. Zero has enough power left to give a parting counterattack as he fades away, finishing Sigma off.
* LettingTheAirOutOfTheBand: A computer variant as described on the page after being once destroyed by Zero.
* LightningBruiser: In most of his (first) forms, Sigma is incredibly swift and agile, and has incredible strength to go with it.
* MagnumOpus: Dr. Cain created Sigma as the pinnacle of Reploid technology (at the time). He was so advanced that it took the Maverick Virus months to corrupt him, and even then his programming managed to appropriate the virus into his own breed of virus.
* TheManBehindTheMonsters: All of the humanoid Sigma's henchmen are all animaloid, save for his various [[TheDragon Dragons]].
* ManipulativeBastard: Before Sigma was even made aware of his newfound viral nature and began infecting reploids left and right to built his forces, Sigma recruited all of his turncoat elites from the Maverick Hunters by playing into their wants and vulnerabilites, with Maverick Hunter X expounding on them.[[note]]Chill Penguin's inferiority complex, Flame Mammoth's pride, Spark Mandrill's gullibility, Sting Chameleon's ego, Launch Octopus's vanity, Armored Armadillo's loyalty, Boomerang Kuwanger's curiosity, and Storm Eagle's reluctance leads it might have been some measure of leverage on him.[[/note]] He'd repeat this in ''X4'' with a short conversation planting seeds of paranoia in the General, in ''X5'' by gaining Dynamo's loyalties despite his being a mercenary, and in ''X7'' when he planted himself into the chain of command of Red Alert. This all is aside from the regular loyalty of Vile, who Sigma's managed to continue to get to side with him out of his own interests despite having ''died'' for him several times. Even without being TheCorruption, just ''talking'' at any length with him seems to be dangerous.
* MeaningfulName:
** The uppercase sigma (Σ) is used in mathematics to represent sums. Sigma was built as the "sum" of all Reploids, the ultimate warrior fit to lead the Maverick Hunters. Becomes ironic once he gets obsessed with evolution.
** Along with Zero's name: [[WordOfGod Keiji Inafune]] [[http://www.capcom-unity.com/s-kill/blog/2008/09/05/inafunesan_answers_your_questions says]] that Sigma and Zero basically represent the idea that nothing is absolute. Sigma was a powerful leader of the Maverick Hunters but after Zero passed the virus to him, his allegiance changed. Circumstances can change anything, and nothing is absolute.
* MightyGlacier: In many of his OneWingedAngel forms, he trades speed and agility for pure power. This is also evident in his first form in ''X6'' where his movements and attacks are extremely slow, but very powerful.
* MirrorMatch: Per his playability in [=DiVE=], he can fight against five different versions of himself during Raid Bosses: Wolf Sigma from ''X1'', Phantom Sigma from ''X4'', Final Form Sigma from ''X4'' (the Gunner Sigma and Earth Sigma phase of the final boss), Final Sigma W from ''X5'', and the Sigma Virus from ''X2''.
* MotiveDecay: Sigma was once a [[InformedAbility stated]] charismatic revolutionary. Upon turning Maverick, his initial goal was for the Reploids to reign over mankind (akin to ComicBook/{{Magneto}}) before he became obsessed with the defeat of the heroes. From ''X2'' onwards, Sigma's goals usually switched between trying to obtain new bodies for himself ([[ManipulativeBastard manipulating others to build them]] such as Dr. Doppler in ''X3'' or trying to take X and Zero's for their technology, such as the former in ''X3'', the latter in ''X5'' via manipulation of the virus, or using Axl to copy their DNA to build an army in ''X7''), [[EarthShatteringKaboom destroy the planet]] (whether via KillSat in ''X4'', ColonyDrop in ''X5'', or SpaceElevator in ''X8''), or just flat-out destroy X and Zero (a constant in every single ''X'' game since ''X1''). Though, really, being corrupted by the Maverick Virus and ''outright merging with it'' probably did not do wonders for his psyche.
* MoreThanMindControl: What makes the [[TheVirus Maverick Virus]] so insidious among fictional infections; it's not an active control that can be [[NoOntologicalInertia broken by killing Sigma]].
** The Maverick Virus ''starts'' by rewriting the infected's cognition, making them genuinely believe and feel that the radical and violent views they come to adopt under Sigma's thrall are in fact their own. This is part of what makes curing them so close to impossible, as it fundamentally changes who they are - the only eventual cure being the Mother Elf, an entity specifically designed to ''manipulate reality using cyberspace'' to finally eradicate the Sigma/Maverick Virus permanently and fix all the affected Reploids.
** In X4, Sigma doesn't need to infect a single member of Repliforce. He just plants the seeds of paranoia, triggers a single incident, and lets the Maverick Hunters and Repliforce go to war of their own accord, all achieved by speaking with General for a matter of ''minutes.''
* MyDeathIsOnlyTheBeginning: As is well-known, destroying Sigma the Reploid only succeeded in unleashing Sigma the virus. This would occur again in ''X8'', where even as he seemed to be dealt his last death, he let slip the little nugget of information that he'd imprinted his personal data in the production of ''all'' Next Generation Reploids, effectively creating ''hundreds'' of Sigmas who would carry on his will whether they realized it or not.
* NeckLift: In ''The Day of Sigma'' OVA, he does this twice, to Zero and then X. Also, during the boss fight with him in ''X8'', he'll do this with one of your characters until you call for help.
* NiceJobBreakingItHero:
** Begun with the very first game, at that. Downplayed in that Sigma was by and large the single most powerful Reploid in existence at the time, he had to be stopped and X was the only one who could do it, but destroying Sigma's body unwittingly just [[MyDeathIsOnlyTheBeginning set him free]], unleashing him in his ''true'' form, whereupon he understood just [[TheVirus what he now was]] and [[ApocalypseHow what was well within his power to achieve]].
** The first part of the EvilPlan in ''X5'', where Sigma baits X and Zero [[MyDeathIsJustTheBeginning into fighting and defeating him at the]] ''[[MyDeathIsJustTheBeginning beginning of the game]]'', spreading TheVirus all over the earth. One should know that it's a trap, since your ArchEnemy wouldn't have let himself get beaten ''that'' easily.
** In a bizarre twist earlier in the series, Sigma's battle with Zero pre-''X''. Sigma's actually TheHero in this scenario, and the whole battle (possibly when Sigma punches Zero's helmet crystal) was the cause of TheVirus passing onto him, triggering his FaceHeelTurn and, in turn, Zero's HeelFaceTurn. Although, it could be that Sigma as a Maverick would be preferable to Zero ''remaining'' a Maverick.
* NiceJobFixingItVillain: Happens twice with Zero -- one detailed in "NiceJobBreakingItHero" above, and another when he had the X-Hunters rebuild Zero after he was destroyed in the first game.
** Sigma debatably does it a third time with Zero in ''X5''. Interested in Zero's potential thanks to the information imparted to him [[spoiler:by Wily]] about Zero's origins, Sigma spends his time trying to re-awaken Zero's Maverick programming and turn him against X instead of outright killing either of them from the beginning. X and Zero ''do'' end up clashing due to mistrust caused by Zero's connection to the Sigma Virus, but Sigma underestimates [[ThePowerOfFriendship the strength of their bond]], with Zero going on to protect X from Sigma's sneak attack and [[HoistByHisOwnPetard deliver the final blow to Sigma]].
** To a lesser extent, he does this to X in the OVA. After he taunts X by strangling Zero in front of him to make him a Reploid-shield and telling X to try to shoot him (knowing that X would hesitate), then gored Zero and throw him away, and then gored X himself, X goes into a brief shutdown but then snaps, and claws Sigma with his glowing hand, causing the trademark scars. It also triggered X's CharacterDevelopment.
** Forcing Eurasia into a ColonyDrop on the Earth would have a major miracle that would pay off a century after his death, since its environmental control system that survived his scheme to awaken Zero's true loyalties and spreading the Sigma Virus on a global scale brought nature back to an area that was once barren, making it a viable alternative for humans compared to Neo Arcadia during the events of ''VideoGame/MegaManZero4''.
* NinjaPirateZombieRobot: His OneWingedAngel in ''X1'' is a wolf robot (and technically zombie too), while his first form in ''X4'' is a GrimReaper robot. [[spoiler:In ''X6'', one of his forms is a robot zombie.]]
* NoHoldsBarredBeatdown: On the ''receiving'' end of this trope back when he was still the Commander of the Maverick Hunters, courtesy of [[spoiler:Zero.]]
* NotMeThisTime: [[ZigZaggingTrope Zig-zagged]] in ''X6''. While Gate was the mastermind behind the "Nightmare" incidents, the whole reason he turned heel in the first place was ''because'' of the Sigma Virus! This may also account for why he resurrected Sigma in the first place, even if the resurrection was [[CameBackWrong completely botched.]]
* OhCrap: Pre-infection, after [[spoiler:Zero]] rips off his arm where he holds his saber, he is shown to be visibly terrified as the Maverick slowly (and menacingly) walks towards him to deliver a viciously sadistic beatdown. And a dream sequence, seen twice in cutscenes, reveals that he is practically screaming for his life.
* OmnicidalManiac: As his sanity withers away and his grudge against the heroes grows, his plans become more destructive and extreme. He goes from wanting to create a world for Reploids (''X1''), to taking over the world (''X3''), to simply destroying it outright (''X4''--''X8''). Considering why he went rogue and who made the Maverick Virus, it's easy to guess the cause of this.
* OneWingedAngel: In every game [[spoiler:except ''X8'']] Sigma is first fought in his humanoid body before moving into a bigger, nastier battle form. A recurring motif of these forms is that Sigma's humanoid face is usually visible in some way, and tends to be the only place he can be damaged.
* OOCIsSeriousBusiness: Sigma is a violent, mindless monster in ''X6'' due to an incomplete resurrection. It shows just how far he's fallen from grace, and how insane Gate was to try resurrecting him at all.
** Sigma sputters in disbelief after his ultimate defeat in ''X8'', unlike other games where he accepted the loss and assured he would return. This implies that he was well aware this was his final act.
* TheParagonAlwaysRebels: He was a honorable commander of Maverick Hunters before he became a Maverick leader.
* PlayingWithFire: His final form in ''X1'' and his first form in ''X3'' both have fire based attacks. His final phase in ''X4'' has three robotic heads with the elements of fire, ice and lightning.
* ThePowerOfHate: Somewhere along the way, Sigma's continued thwarting by the Maverick Hunters began to strike a sour note, though Sigma usually manages to [[AffablyEvil hide it well]]. He revels in the fact that, prior to ''X5'', he met an interesting character [[spoiler:(i.e. Wily)]] who hated X as much as he did, and [[spoiler:his zombie form in ''X6'' does little more than howl in remembrance of his hatred for X and Zero.]]
* PragmaticVillainy: Disapproves of Berkana's actions from ''Xtreme 2'', because she acted [[DragonWithAnAgenda for her own gain]] (rather than his).
* TheProfessor: He uses this title as an alias in ''X7''.
* PromotedToPlayable: After almost 30 years since his debut, Sigma finally gets to be playable in ''[=DiVE=]'' as of July 1st, 2020.
** MeaningfulReleaseDate: This date was not as random as it seems, other than rounding out a new month with a new character. [[AllThereInTheManual According to the PC port's manual]], the Day of Sigma took place in early July.
** ''[=MvCI=]'' was also his first overall playable appearance, predating his playability in his home series by a few years.
* ProperlyParanoid: When trying to convince General to go maverick, he explains that humanity intends to destroy any Reploid that doesn't obey them perfectly. Come the ''[[VideoGame/MegaManZero Zero]]'' series, and especially with the character of Dr. Weil, and it shows that Sigma was pretty much spot on with his assessment. Ironically, [[SelfFulfillingProphecy this was probably due to Reploids constantly rebelling at the slightest provocation. Often due to viruses. Which he spread.]]
* PunchPunchPunchUhOh: In a flashback scene in ''X4'', [[spoiler:Sigma fights Zero and seems to be getting the upper hand, until Zero cuts off Sigma's arm before [[NoHoldsBarredBeatdown beating him into a pulp]]. Sigma only wins when Zero's head crystal suddenly glows and gives him a headache, allowing Sigma to knock out Zero with a punch]].
* RageQuit: His entire plan in ''X8'' is him relocating himself and New Gen Reploids to the moon, due to the earth being torn apart after so many prolonged wars, and then he's going to demolish the earth outright to start anew.
* RightHandAttackDog: At the end of ''X1'', he sics his [[SavageWolves robot pet Velguarder]] on X before confronting him personally.
* {{Sadist}}: Has some shades of this when taunting Zero about [[spoiler:Iris' death]].
* RougeAnglesOfSatin: This happens when Sigma enters his [[OneWingedAngel final phase]] in ''VideoGame/MegaManX6'', with many of his words being misspelled. Examples include "battle" > "baddle", "just" > "jusd", "begun" > "begunn", and "Just die!!!" > "Jusdie!!!"
* SanitySlippage: With each subsequent game and each subsequent resurrection, Sigma's sanity began to gradually erode. Over the course of the series, he goes from a charismatic, sophisticated DiabolicalMastermind to little more than a brutish thug driven only by his hatred for the heroes, but retaining enough of his intelligence to be extremely dangerous. One can probably guess ''why'' his sanity was degrading, merging with a virus made by a insane mad scientist and then spending a lot of time jumping between bodies and hanging out outside of a body, nevermind the whole HiveMind thing that comes with being a virus, probably did not do wonders for his mental state.
* ScarsAreForever: No matter what body he uses, the trademark scars over his eyes are left intact. Even when he gets entirely new bodies with new heads, he always retains these scars as a sort of trademark. How he obtained them varies between continuities: a flashback in ''X4'' attributes the scars to battle damage from Maverick Zero's NoHoldsBarredBeatdown, while the ''The Day of Σ'' shows X scratching Sigma over the eyes with a [[Anime/MobileFighterGGundam Shining Finger]]-like attack, and both the Iwamoto Yoshihiro manga as well as the novelization for ''X1'' has him scar himself with the heat from his cannons as he wages war against humanity.
* SecondaryColorNemesis: Best seen in official artwork, but his standard outfit consists of a green body armor with purple sleeves and pants.
* SelfFulfillingProphecy: Sigma predicts that humanity will scrap any Reploid that doesn't obey them perfectly, so he launches numerous genocidal campaigns against the humans. Even if Sigma might be right, as shown in the ''Zero'' series, what he did definitely contributed to his prediction.
* ShadowedFaceGlowingEyes: Sigma's first form in ''X4'' has a pretty clear parallel to the grim reaper, with glowing yellow eyes from a face hidden by a dark cloak, while also floating and carrying around a huge scythe.
* ShockAndAwe: His final form in ''X1'' and his first form in ''X2'' both make use of thunder-based attacks. In ''X4'', one of his final phase's moves involves three heads with the powers of fire, ice and lightning.
* ShotgunsAreJustBetter: His main weapon in ''X7'' is a double-barreled shotgun.
* SignatureLaugh: "Hee Hee Hee!"
* SinisterScythe: Trades in his trademark LaserBlade for one of these in ''X4'' to go with his overall GrimReaper motif.
* SlasherSmile: He seems to always have a manic grin on his face.
* SlouchOfVillainy: He does this in ''X8''.
* TheSociopath: Thanks to the Maverick Virus, Sigma went from a noble-hearted Maverick Hunter to a ruthless monster who manipulates other Reploids into doing what he wants, kills countless innocent people, and sadistically terrorizes X and Zero time and time again. He's even more of a sociopath in ''Maverick Hunter X'' because he chose to become evil, and didn't need to be infected with a virus to go Maverick.
* SpannerInTheWorks: Unwittingly defeats Wily's plan to have Zero wreck havoc on the world, in the process setting up Zero's HeelFaceTurn. However, it also leads to Sigma's own turn. [[spoiler: In X5, it's implied that Wily (whose somehow still around) uses this to his advantage and upgrades Sigma instead)]]
* SpikesOfVillainy: Added these to his armor after his FaceHeelTurn. They frequently adorn his armor in his later incarnations.
* TakingYouWithMe: He tries to take both Zero and X down with him in ''X5'' before Zero fires one last shot, completely destroying him. [[spoiler:Sigma half-succeeded; he did mortally wound X, but X is then repaired by Dr. Light afterwards.]]
* ThisCannotBe: At the end of ''X1'':
-->'''Sigma:''' No!!! It's not possible! I'm a Reploid! I can't be destroyed by you! Why, X?! Why have you done this us?! Without the humans, my Reploid brothers could have ushered in a new age...
* ThrowingYourShieldAlwaysWorks: Sigma in ''X3'' throws his shield like a boomerang once his health gets low enough.
* TookALevelInDumbass: [[spoiler:In ''X6'', to the point where he speaks in broken dialogue, and in ''X8'', where he's being used by Lumine.]]
* TyphoidMary: At some point Sigma bonds with the Maverick virus and becomes a living virus himself. He even exploits this in ''X5'', sacrificing one of his bodies in order to infect the entire world.
* TheUnfettered: He'll do whatever it takes to ensure the extinction of humanity comes to fruition, and doesn't give a damn about the consequences of his actions.
* UnexplainedRecovery: Subverted for most of his reappearances besides ''X4''. There is literally no explanation for his recovery here, though some fans believe it's a carry-over of his resurrection in ''Xtreme 2'' by Berkana.
* UnfinishedUntestedUsedAnyway: A recurring problem Sigma suffers from is that several of his awe-inspiring OneWingedAngel forms aren't actually finished being constructed yet, most notably in ''X5'' where he outright admits it's not ready [[spoiler:despite Dr. Wily's work]], and some of the ones that are haven't even been put through their paces in testing like in ''X3''. But X/Zero envitably always blow up his humanoid form for the day before then, so might as well break it in (and break it down) against the best.
* UnwittingPawn: If Lumine's words are to be believed, [[spoiler:Sigma was actually being used by Lumine in ''X8'', particularly with the plan to migrate to the moon using the Jakob Orbital Elevator. Played with in that it's confusing about who's using who; while Lumine might be right, he still has Sigma's DNA put into his Copy Chip, and thus possesses Sigma's will and plans; basically Lumine keeps furthering Sigma's plan, even if he still retains his individuality, including making Sigma his pawn.]]
* VillainDecay: [[InvokedTrope Invoked]]. After Sigma truly died in ''X5'', his botched resurrection [[spoiler:by Gate]] led to Sigma steadily losing his own villainy more and more. By the time ''X8'' rolls around, he's completely abandoned his own mission and decides to just wipe out the Earth and start his own society on the moon, a plan so rife with holes that you ''know'' all ability to rationalize has left him. It doesn't go unnoticed, either. Starting with [[spoiler:''X6'']], X and Zero no longer regard Sigma as any kind of WorthyOpponent, and only seem to consider him a threat from little beyond his destructive potential if left to his own devices.
* VillainOpeningScene:
** In the opening cutscene of X's ''X4'' story, a cloaked Sigma is having a discussion with General about the Maverick Hunters, trying to convince him to fight against and destroy them.
** In the opening cutscene of ''X5'', Sigma has a discussion with Dynamo to spread TheVirus across Earth.
* VillainTakesAnInterest: In ''X4'' after taking down Maverick Zero, Sigma orders his troops to retrieve him so he could study Zero. ''Maverick Hunter X'' has him intrigued by the limitless potential X possesses, believing it would be the key to Reploid evolution.
* TheVirus: His true form, after the Maverick Virus from Zero's Capsule merged with him. According to ''Mega Man Zero Official Complete Works'' the true form of the Sigma Virus is the Suffering Circuit (it implies that Dr. Wily has stolen the data of said circuit from Dr. Light), which gives X and all the Reploids the ability to decide right and wrong for themselves; the virus corrupted both his DNA and said Suffering Circuit, creating a new virus strand that is alive with his consciousness.
* WaveMotionGun: Uses giant laser cannons in several of his battles such as ''X3'', ''X6'', and ''X7''.
* WeakenedByTheLight: In ''X8'', his real body is weak against Optic Sunflower's light-based weapons. Definitely symbolic.
* WeaksauceWeakness: His OneWingedAngel forms tend to suffer this in one way or another. Worst possible contender? Splash Laser, a ''literal BubbleGun''.
* WeakToFire: His cloaked reaper form in ''X4'' can only be harmed by the fire-based weapons obtained from Magma Dragoon, nothing else will harm him. A LogicalWeakness considering that his cloak burns and catches on fire when he's hit by fire weapons.
* WellIntentionedExtremist: He started off as this in the first game, where he wanted to remove humans from the equation out of a genuine desire to allow Reploids to grow and evolve while realizing their true potential before devolving into a murderous lunatic in the later games.
* WhileRomeBurns: At the end of ''The Day of Sigma'', he eagerly awaits X to reach him while evilly laughing as Abel City is devastated by his missiles.
* WorldsStrongestMan: At the time of his creation, Sigma was ''the'' most advanced and powerful Reploid produced, befitting his position as the to-be leader of the Maverick Hunters (meaning he would be the last line of defense against any Maverick) and equipped with the most advanced anti-virus systems of the day. He could even fight on par with an AxCrazy [[spoiler:Zero]], and with X still deep in his ReluctantWarrior phase and [[spoiler:Zero]] losing some of his lethality after going sane, Sigma was essentially the most powerful being on the planet. Sigma only lost this title as X grew into his true power while Sigma began to fall into VillainDecay from repeated defeats and deaths.
* WolverineClaws: Uses LaserBlade variants as his weapon for ''X2'' and ''Xtreme 2''.
* WorthyOpponent: Though both the main protagonists would be loathe to admit it, the one thing about Sigma nobody ''dared'' to ever underestimate of the Maverick commander in the main pentalogy was his raw power and combat skill, and he is perhaps the only character to consistently be a match for X and Zero. Even as far as ''X8'', his form is acknowledged as more or less the the most sturdy and powerful form a New Gen Reploid could take to avoid harm.
* YoureInsane: Called this by Vile in ''Maverick Hunter X'' for planning to take advantage of X's potential upon starting his rebellion.
[[/folder]]

* CharClone: Has most of his traits from Char's Counterattack as a Dark Messiah judging humanity by rebelling against them as another race in a much brutal fashion and even his legacy goes on afterwards transcending to another plane of existence and transferring his another kind into another body. He is shown to be {{manipulative|bastard}} to his allies and treats them nothing more but a piece of pawn in his game and even develops a rivalry with the blue schemed protagonist throughout the series.

* EvilutionaryBiologist: He follows the robotic version of this, especially in ''Maverick Hunter X,'' where he wants to see the true potential in Reploidkind. His plan is to prove this potential by pushing X to his limits.
-->'''Sigma:''' "Evolution requires sacrifice."

* AFatherToHisMen: Back when he was still commander of the Maverick Hunters, when they managed to corner the single rogue maverick [[spoiler:(Zero)]], he insisted going in by himself as he couldn't bear the idea of losing more of his men.

* FlingALightIntoTheFuture: A villainous take on this. [[spoiler: In X8, Sigma seemed to finally acknowledge his increasing decay and limited time, so he hijacked the production of New Generation Reploids to instill his personal data across all of them -- save for Axl, who narrowly avoided the impromptu "adoption". While Sigma's next stand appeared to have finally been his last, it didn't matter, because he effectively created an ''entire line of Sigmas'' to succeed him. Unfortunately for him, all of this effort is eventually undone by the Mother Elf.]]

** [[spoiler:''X6'' is also an interesting case in that Gate is still the true mastermind of the game, as Sigma's current incarnation is an unstable zombie who was revived simply because Gate thought he needed a backup plan against X and Zero (plus some possible influence from the Maverick/Zero Virus). He just kills Gate after his defeat, and X and Zero go after him because... well, it's Sigma.]]
*** X practically lampshades Sigma's presence [[spoiler:in ''X6'']]:
--> '''X''': Sigma... we don't have time to deal with you. We need to rebuild our world and I can't let you get in our way. It doesn't matter how many times you'll come back... I'll beat you!

* MeaningfulName: The uppercase sigma (Σ) is used in mathematics to represent sums. Sigma was built as the "sum" of all Reploids, the ultimate warrior fit to lead the Maverick Hunters. Becomes ironic once he gets obsessed with evolution.

* MoreThanMindControl: What makes the [[TheVirus Maverick Virus]] so insidious among fictional infections; it's not an active control that can be [[NoOntologicalInertia broken by killing Sigma]]. The Maverick Virus ''starts'' by rewriting the infected's cognition, making them genuinely believe and feel that the radical and violent views they come to adopt under Sigma's thrall are in fact their own. This is part of what makes curing them so close to impossible, as it fundamentally changes who they are - the only eventual cure being the Mother Elf, an entity specifically designed to ''manipulate reality using cyberspace'' to finally eradicate the Sigma/Maverick Virus permanently and fix all the affected Reploids.
** Played straight in the more traditional sense in X4 -- namely, in that Sigma doesn't need to infect a single member of Repliforce. He just plants the seeds of paranoia, triggers a single incident, and lets the Maverick Hunters and Repliforce go to war of their own accord, all achieved by speaking with General for a matter of ''minutes.''

* PunchPunchPunchUhOh: In a flashback scene in ''X4'', Sigma fights Zero and seems to be getting the upper hand, until Zero cuts off Sigma's arm before [[NoHoldsBarredBeatdown beating him into a pulp]]. Sigma only wins when Zero's head crystal suddenly glows and gives him a headache, allowing Sigma to knock out Zero with a punch.

* WorldsStrongestMan: At the time of his creation, Sigma was ''the'' most advanced and powerful Reploid produced, befitting his position as the to-be leader of the Maverick Hunters (meaning he would be the last line of defense against any Maverick) and equipped with the most advanced anti-virus systems of the day. He could even fight on par with an AxCrazy Zero, and with X still deep in his ReluctantWarrior phase and Zero losing some of his lethality after going sane, Sigma was essentially the most powerful being on the planet. Sigma only lost this title as X grew into his true power while Sigma began to fall into VillainDecay from repeated defeats and deaths.

* AuthorityEqualsAsskicking: Dr. Cain built Sigma to be the leader of the Maverick Hunters and consequently to have the power to match the post. At the time of his creation, Sigma was ''the'' most advanced Reploid in the world both on a physical level and with the most advanced anti-virus software installed that would, in theory, prevent him from going Maverick and thus turning that power against humanity. He continues to hold true with this more or less as the leader of the Mavericks.

* MyDeathIsOnlyTheBeginning: As is well-known, destroying Sigma the Reploid only succeeded in unleashing Sigma the virus. This would occur again in ''X8'', where even as he seemed to be dealt his last death, he let slip the little nuget of information that he'd imprinted his personal data in the production of ''all'' Next Generation Reploids, effectively creating ''hundreds'' of Sigmas who would carry on his will whether they realized it or not.

** Begun with the very first game, at that. Downplayed in that Sigma was by and large the single most powerful reploid in existence at the time, he had to be stopped and X was the only one who could do it, but destroying Sigma's body unwittingly just [[MyDeathIsOnlyTheBeginning set him free]], unleashing him in his ''true'' form, whereupon he understood just [[TheVirus what he now was]] and [[ApocalypseHow what was well within his power to achieve]].

* NotMeThisTime: [[ZigZaggingTrope Zig-zagged]] in ''X6''. While Gate was the mastermind behind the "Nightmare" incidents, the whole reason he turned heel in the first place was ''because'' of the Sigma virus! This may also account for why he resurrected Sigma in the first place, even if the resurrection was [[CameBackWrong completely botched.]]

[[quoteright:400:https://static.tvtropes.org/pmwiki/pub/images/megamanxdive_sigma.png]]

* ANaziByAnyOtherName: For the first few games, his attitude about humans can be summarized as "the inferior need to be exterminated so the superior can thrive".

* CloningBlues: In the ''X1'' novelization, Sigma has a freakout when he discovers that he and all other reploids were made from X's designs making them "flawed copies." This of course leads to his rebellion.

* FantasticRacism: He believes humans to be inferior to Reploids, and most of his plans through the series involve the slaughtering of the human race.

[[Characters/MegaManXHeroes Heroes]] ([[Characters/MegaManXX X]] | [[Characters/MegaManXZero Zero]]) | [[Characters/MegaManXVillains Villains]] ('''Sigma''') | [[Characters/MegaManXMaverickBosses Maverick Bosses]] | [[Characters/MegaManXSupportingCast Supporting Cast]]]]]]-]

Instead become simply being infected, however, Sigma’s advanced nature caused him to became one with the virus, and the process turned him into a murderously insane maniac bent on ending the human race. He’s appeared in many bodies throughout the series, and Sigma is never usually the same each time. No matter what form he takes, however, one thing is always consistent: as long as the Sigma Virus lives on, Sigma lives on.

The [[BigBad primary antagonist]] of the ''X'' series. {{Bald|ofevil}}, scarred, {{manipulative|bastard}}, and murderously insane; [[FaceHeelTurn the former leader of the Maverick Hunters]] now seeks nothing less than the destruction of the people he was built to protect.

* OneWingedAngel: In every game [[spoiler:except ''X8'']] Sigma is first fought in his humanoid body before moving into a bigger, nastier battle form.

* GoneHorriblyRight: Sigma was designed with the most advanced anti-virus software at the time of his creation in the hopes he would be able to fight off any infection. When he ''was'' infected by the Maverick Virus [[spoiler:due to his battle with Zero]], his programming did indeed fight off the infection and instead [[FusionDance merged with it]], [[DeathOfPersonality destroying his old personality]] and becoming a new, even more dangerous virus.

* AmbiguousSituation: From the first game's manual, it was always established that he led his Maverick rebellion as he believed that humans were limiting the evolution of Reploids. However, later games would establish that Sigma went Maverick after his fateful encounter with Zero, which would get the former infected with the Maverick Virus to merge with Sigma's mind to form the Sigma Virus. It is therefore unclear whether Sigma turned evil entirely because of the virus messing with his mind or Sigma was always resentful of humans with the virus merely giving him the means to carry out his rebellion. However, some of his characterizations pre-virus (in the X4 flashback and an archive of his old data on Dive) showcase him to be fairly reasonable.

** The second ''VideoGame/MegaManXDive'' Halloween event, ironically enough, gives a glimpse of what Sigma was like before he was corrupted - a genuinely pleasant and nice guy who was supportive of his comrades and subordinates, and even a bit playful at times, in a good way. Both [=RiCO=] and [=ViA=] can't help but feel a bit of whiplash from meeting the series BigBad from before he became evil.

** [[spoiler:''X6'' is also an interesting case in that Gate is still the true mastermind of the game, as Sigma's current incarnation is an unstable zombie. He just kills Gate after his defeat, and X and Zero go after him because... well, it's Sigma.]]

* AmbiguousSituation: From the first game's manual, it was always established that he led his Maverick rebellion as he believed that humans were limiting the evolution of Reploids. However, later games would establish that Sigma went Maverick after his fateful encounter with Zero, which would get the former infected with the Zero Virus which would merge with Sigma's DNA to form the Sigma Virus. It is therefore unclear whether Sigma turned evil entirely because of the Virus messing with his mind or Sigma was always resentful of humans with the Virus merely giving him the means to carry out his rebellion. However, some of his characterizations pre-virus (in the X4 flashback and an archive of his old data on Dive) showcase him to be fairly reasonable.

* AnthropomorphicPersonification: He's the living will of the Maverick Virus. It's heavily implied that [[AsLongAsThereIsEvil as long as the Maverick Virus exists there's always a chance that he could return.]]

* LanternJawOfJustice: Inverted with his massive Chin of Villainy.

** Zero is the one who infected Sigma with the virus in the first place, and [[TheAtoner is greatly disturbed by what he did to the former Maverick Hunter]]. On Sigma's end, he indirectly causes [[spoiler:[[TheLostLenore Iris' death]]]], even [[KickTheDog mocking Zero about it]], and later goes along with Dr. Wily's posthumous plan to turn Zero into the monster he was meant to be.