* EVERYONE in ''VideoGame/ShinMegamiTenseiIIINocturne''. Hikawa was evil to begin with, then Isamu sacrifices Hijiri to summon Noah and Chiaki does the same thing to Futomimi to summon Baal Avatar.
** In ''VideoGame/{{Persona 4}}'' [[UpdatedRerelease Golden]], ''the protagonist himself'' can go through one if he makes friends with [[spoiler: Tohru Adachi]] before realizing he's the killer, [[spoiler: confronts him (instead of keeping his thoughts to himself]] and ''then'' [[spoiler: aids Adachi via destroying crucial evidence.]] [[spoiler: This unlocks the "Accomplice ending": it has Adachi becoming a KarmaHoudini for the murders and even ''taunting the protagonist'' before he (the MC) leaves Inaba.]] Doing so actually gives a decent reward for a NewGamePlus. At the very least, it's much more cost effetive than what you get in the true ending.
* The supposed FaceHeelTurn of Ralgha "Hobbes" nar Hhallas in ''VideoGame/WingCommander III'' didn't work for many fans of that series who have only played the PC version (the console versions used bigger [=CDs=] than computers of the time, and could thus fit the explanation cutscene into the game; the {{novelization}} also covers the explanation). In this case, he was an (unwitting) [[TheMole mole]].
* Sorbet in ''MagicalStarsign'' fakes one as part of an elaborate plan to trick the Big Bad, and it's so convincing that even your party falls for it...unfortunately, you waltz in just as her plan is about to come to fruition.
** Fortunately, it wasn't the best thought out plan anyway...
* Ghaleon in ''VideoGame/LunarTheSilverStar''.
* Queen Ashlelei in ''VideoGame/{{Malicious}}'', the once great and respectable ruler turned into a ravaging war demoness after a series of traumatic events, her two chilren being killed by her husband, King Eldrake their father, in front of her is one of these events to name.
* The player's wingman Solo-Wing Pixy does this in ''AceCombat Zero'' after witnessing the horrors of war, including the enemy dropping ''seven'' nuclear bombs ''on their own soil''.
* The [[BigBad villain]] from the very first ''[[VideoGame/FinalFantasyI Final Fantasy]]'', Garland's {{backstory}} states that he was once a famous hero. [[FaceHeelTurn That all changed]] when he kidnapped [[EverythingsBetterWithPrincesses the princess of Cornelia]] in a bid to take over the kingdom.
* Sephiroth in ''VideoGame/FinalFantasyVII'' goes through a particularly malignant FaceHeelTurn in the main character Cloud's [[StartOfDarkness flashback]]...the awesomeness of which also made him the ultimate DracoInLeatherPants character.
** The PSP game ''CrisisCore'' (where you play as Zack, the guy Cloud absorbed the personality of) portrays this moment at the end. You even get to see Sephiroth before he went batshit. There's quite a few of the villains that do a HeelFaceTurn.
* Seifer in ''VideoGame/FinalFantasyVIII'' goes through a much more low-key version of this as well.
* In the 11th chapter of the first SakuraWars game, [[spoiler: Ayame Fujieda]].
* Kain from ''VideoGame/FinalFantasyIV'', partly because of brainwashing, but also partly because of his envy for his best friends Cecil, who was the boyfriend of the girl he had a crush on.
* In ''MOTHER 3'', [[spoiler:Claus is brainwashed by Porky and becomes the Masked Man (also the FinalBoss)]].
* Hardin and his cronies from ''[[FireEmblemAkaneia Fire Emblem: Mystery of the Emblem]]''. In ''[[UpdatedRerelease New Mystery of the Emblem]]'', his cronies can be [[HeelFaceTurn re-recruited]]. [[BrainwashedAndCrazy Hardin]] himself, however, cannot.
** Alvis from ''[[FireEmblemJugdral Fire Emblem: Genealogy of the Holy War]]'' though he was more of an AloofAlly to your party.
*** Orson from ''FireEmblemTheSacredStones'', in a LoveMakesYouCrazy way.
* In ''VideoGame/SuperRobotWarsOriginalGeneration'' and ''VideoGame/SuperRobotWarsAlpha'' [[spoiler:Ingram Prisken, leader of the SRX team and Ryusei's mentor, reveals halfway through the game that he is an alien spy who was trying to strengthen the earthlings so they would make better weapons for the Balmar. He afterwards becomes ThatOneBoss.]]
** Captain Lee in ''VideoGame/SuperRobotWarsOriginalGeneration 2'' pulls one of these, after spending his entire time [[KickTheDog kicking dogs]]. Even a dead family, doesn't protect him.
* Jerry Ying from the JohnWoo game ''{{Stranglehold}}'', who starts out as Tequila's partner and ally inside Wong's Dragon Claw syndicate, only to [[spoiler:[[GoingNative go native during the Chicago History Museum stage]] and carry out Wong's orders to kill Tequila and [[OffingTheOffspring Billie, Wong's own daughter]]. Tequila survives, but Billie isn't so lucky, setting up a furious showdown between partners as Tequila seeks vengeance for Billie]].
* ''Everybody'' in ''{{Warcraft}}''. The only creatures who were evil from the start are the [[EldritchAbomination Old Gods]] of Azeroth and some of their servants. Everybody else started good and was corrupted by some means.
** Sargeras by [[HeWhoFightsMonsters fighting a bit too many demons.]]
** The Eredar and the Orcs started out as peaceful {{Magitek}} and shamanistic races, respectively, but were corrupted by promises of power.
** Pictured in the main page: Arthas in ''{{Warcraft}} III'' falls to due to to Lich King's EvilPlan.
** Vincent Godfrey is interesting in the fact that he Face Heel Turns twice without ever commiting a HeelFaceTurn. When you first start the Worgen starting experience he's a loyal Gilnean citizen and is seemingly important in helping cure your character of the Worgen curse. He then Face Heel Turns against you when he finds out that King Greymane is a Worgen and attempts to ransom him to the Forsaken until rescued by the player character. After killing himself, he is risen as a Forsaken and helps the Forsaken players in helping fight Gilnean Rebels in Pyrewood Village before he the betrays the Forsaken and sets up shop in Shadowfang Keep.
** The Zandalari trolls have turned hostile after their homeland on Zandalar Isle is destroyed in the ''Cataclysm'', and by the time of ''Mists of Pandaria'', they have allied with the malevolent Thunder King.
* Beat in ''VideoGame/TheWorldEndsWithYou'' does a Face Heel Turn ''and'' [[HeelFaceTurn the opposite]].
** Technically, Joshua also had a Face Heel Turn, but he was that way from the beginning; he was just acting.
* ''BatenKaitos'' has a fantastic example in the first game, where [[spoiler:''the main character'', Kalas]] pulls a FaceHeelTurn. [[spoiler:He later pulls a HeelFaceTurn, though]].
* Sialeeds in ''VideoGame/SuikodenV''.
** Jowy in ''VideoGame/SuikodenII''.
* The Boss in ''MetalGearSolid3: Snake Eater'', who switches from United States allegiances to the Soviet Union. [[spoiler: It turns out that The Boss was really doing this to help the United States regain The Philosopher's Legacy. ''Naked Snake'' kills her, taking her position as Big Boss, only afterwards learning the truth.]]
** It's more of a FakeDefector really.
** In a sense, both Big Boss and Zero certainly qualify with regard to the entire series. One became the leader who of a mercenary nation who start war and is the antagonist for the first two game, while Zero and his Patriots are the antagonist behind the other numbered games. All because the Boss died.
** A huge Face Heel Turn takes place in ''MetalGearSolid2'' when [[spoiler: most of the characters on Raiden's Codec turn out to be part of a computer system training him to become an artificial Solid Snake, a wonderful example of ''TheComputerIsYourFriend'' that continues in ''MetalGearSolid4'']]. Giant metaphysical discussions and a ''MotiveRant'' ensue.
* [[spoiler:Judith Mossman ]] from ''VideoGame/HalfLife2''. She [[spoiler: Does it so much you'll have whiplash by the final level.]]
* Riku from ''VideoGame/KingdomHearts'' was, unknown to his best friend Sora, gradually making the FaceHeelTurn, desperate to [[IDidWhatIHadToDo save Kairi through whatever means possible]]. He ends up going a similar way as Kain from ''VideoGame/FinalFantasyIV'', complete with a return to the good side and a MyGodWhatHaveIDone.
* In ''Pokémon Red and Blue'', a Team Rocket Grunt on Nugget Bridge asks you to do this. However, he is just kidding.
* Mario plays the antagonist in ''Franchise/DonkeyKong Junior''.
** Speaking of Mario games: at the end of ''PaperMarioTheThousandYearDoor'', the BigBad asks you to do this. You can actually say yes - it gives you a NonstandardGameOver.
** In ''MarioAndLuigiSuperstarSaga'' [[spoiler: Birdo]] pulls out a FHT after helping the Mario Bros. earlier. Another FHT happens in ''[[MarioAndLuigiBowsersInsideStory Bowser's Inside Story]]'', when [[spoiler: Sergeant Guy, Corporal Paraplonk and Private Goomp]] betray [[VillainProtagonist Bowser]] and switch over to [[BigBad Fawful's]] side.
* The player character and his FiveManBand in ''Mechwarrior 4: Vengeance'' becomes the FiveBadBand in the ''Black Knight'' expansion.
* Sigma from ''VideoGame/MegaManX'' was originally the leader of the Maverick Hunters before he caught (and soon after became) TheVirus from Zero and decided to go evil and declare war against mankind. Zero, in turn, does a HeelFaceTurn, caused by said virus transfer via a punch to the forehead.
** And in a turnaround, [[spoiler:the title character]] of ''VideoGame/MegaManX'' was supposed to make a FaceHeelTurn into the BigBad of the ''VideoGame/MegaManZero'' series. [[FauxShadow Emphasis on]] ''[[FauxShadow supposed]]'', thanks to a ContinuitySnarl.
* The MegaManZero series gives us Elpizo in the second game.
* Colonel from ''VideoGame/MegaManBattleNetwork'' was previously the Navi of the leader of a team that aimed to purge Nebula from the Net before doing a FaceHeelTurn.
* In ''Hero Senki'' [[spoiler: Gilliam Yeager, the Ally with the most powerful unit at the start of the game is the final boss. He becomes TheAtoner after he jumps universes though]]
* It's stated that [[spoiler: Gol and Maia]] from the original ''JakAndDaxter'' were good once, but exposure to [[BadPowersBadPeople Dark]] [[GreenRocks Eco]] caused a faceheel before the beginning of the game.
* [[spoiler: Bastila]] in ''KnightsOfTheOldRepublic''. Can also happen to anyone you have a high influence with in the sequel, if you're [[KarmaMeter going]] [[VideogameCrueltyPotential dark]].
* Arguably, both [[spoiler: Kreia]] and [[spoiler: Atris]] in ''KnightsOfTheOldRepublic II''. Yes, both were already Grade-A bitchy, but neither was definitively evil until the end of the game.
** The Jedi Masters could easily be interpreted as this.
* In ''StarOceanTheLastHope'', [[spoiler: Faize pulls a big one. He doesn't just become a villain, he becomes ''the final boss''.]]
* ''[[{{Gradius}} Gradius ReBirth]]'' retcons Venom into an example of this--he starts off as James's CO, but becomes a heel after you complete the game's third loop. He goes on to become the BigBad of ''[[GaidenGame Nemesis 2]]'' and ''[[GaidenGame 3]]'', two lesser-known installments released on the MSX over 20 years before.
* Kazuya from ''VideoGame/{{Tekken}}''. He was originally a Ryu-esque cookie-cutter hero [[spoiler: but eventually let the devil consume him and became (arguable) one of the bad guys]]. By the beginning of the sixth game, he had plans for world domination.
** And there's also [[spoiler: Kazuya's son with Jun]], Jin Kazama. He was TheHero for about three games, then at the beginning of the sixth game, takes over the mega corporation and uses it to start WorldWarIII and try to TakeOverTheWorld, which prompts Kazuya to speed up his plan for world domination.
*** To be fair though, it's heavilly implied that Jin is doing this just so that he can kill off his own bloodline by any means necessary, bringing both Kazuya and Heihachi out for him to fight up front. Though [[spoiler:no one is aware of Lars, Heihachi's illegitimate son.]] Though quite villainous and menacing still, this does make Jin more of an AntiHero, or an AntiVillain maybe.
** The entire Mishima Zaibatsu, by '''VideoGame/{{Tekken}} 6'', are caught in an endless ''HeelFaceRevolvingDoor''. It would be boring to watch this over and over again, and the more interesting characters seem on the periphery by now, but alas, Namco takes the position that ''ElitesAreMoreGlamorous''.
* In ''VideoGame/NeverwinterNights2'', [[spoiler:Neeshka, Sand and Qara will betray you at the end of the game if their influence is too low. And if you manage to keep Sand, Qara will automatically betray you and vice versa.]]
** And [[spoiler:Bishop]] does so even earlier. He never was much of a Face to begin with. [[spoiler:Though he ''can'' be persuaded to [[ScrewThisImOuttaHere back out of]] the final fight.]]
** [[spoiler:Alternatively, '''you''' can do this by accepting the BigBad's offer. In doing so you [[MoralEventHorizon slaughter your former comrades and bring about the apocalypse]].]]
* [[spoiler:Aribeth de Tylmarande]] of VideoGame/NeverwinterNights does this. [[spoiler:Bastila]] was [[spoiler:Aribeth]] dropped into an alternate setting and given a more active role in the story.
* In the backstory for ''VideoGame/StarFox64'', Pigma Dengar betrayed James [=McCloud=] to Andross. Later in the series, Andross's grandson Dash Bowman undergoes one of these in two alternate endings for ''Star Fox: Command''.
* In a rare example of the ''player'' doing this, the original ''StreetsOfRage'' has, near the end of Round 8, Mr. X asking you if you want to join him. In a 2-player game, if one player answers "yes" while the other answers "no," they will fight to the death, with the winner being asked again if they want to join. If the winner says no, and defeats Mr. X, the winner gets an alternate ending in which he or she becomes the new syndicate leader.
* Common in the ''VideoGame/GrandTheftAuto'' series, though considering you are usually playing a VillainProtagonist it's usually more a case of Heel Heel Turn.
** Catalina in the opening sequence of ''VideoGame/GrandTheftAutoIII''.
** [[spoiler:Salvatore Leone in the mission Last Requests]] in ''VideoGame/GrandTheftAutoIII''.
** [[spoiler:Lance Vance]] in ''[[VideoGame/GrandTheftAutoViceCity Vice City]]''.
** [[spoiler:Big Smoke and Ryder]] in ''[[VideoGame/GrandTheftAutoSanAndreas San Andreas]]''.
** [[spoiler:Dmitri Rascalov and Michelle]] in ''VideoGame/GrandTheftAutoIV''.
*** [[spoiler:Darko Brevic]] in the backstory of ''VideoGame/GrandTheftAutoIV''.
* ''VideoGame/SoulCalibur'': someone is doing one of these every five minutes. We have Siegfried, who did a Face to Heel (before the series even started) to Face to Heel to Face to WellIntentionedExtremist Heel...and then back to Face again. Then there's Yun-Seong, who isn't all the way there yet, but he's getting there. Raphael, who did a Face Heel turn from 2 to 3, and did a Heel/Worse Heel turn from 3 to 4. Sophitia has done this in 4: arguably she has a good reason, but as she has been infused with the power of Soul Edge, there's nothing saying that she might not like this state of affairs later on. Then you've got Pyrrha, who went from Face to Heel (somewhat against her will) and then back to Face, and then BACK to Heel, before finally settling on Face.
* At the end of the ''VideoGame/{{Fallout 3}}'' dlc ''Operation: Anchorage'', [[spoiler:an Outcast defender named Sibley gets disgusted that his superior is sharing the spoils with a "local" (you) and attempts to kill him unless you stop him.]]
** Also, in the main game, [[spoiler:Anna Holt is the one who tells the enclave about the project purity activation code, after she's captured, and later shows up as a scientist working for them in their base. Oddly enough, you still get bad karma for killing her]].
* In the ''{{Halo}}'' series, your buddy friend, 343 Guilty Spark does this on two occasions. In the first Halo, he helps you to activate the ring until Cortana stops him, saying that doing so will kill everyone. 343 Guilty Spark sees this as breaking protocol and then tries to kill you. This also happens in Halo 3, where you go to destroy the ark. 343 starts going off at you again and then kills Seargent Johnson.[[spoiler: You quickly kill 343 Guilty Spark with Johnson's spartan laser.]]
* In ''Call of Duty: Modern Warfare 2'', [[spoiler: Gen. Shepherd has one near the end of the game and kills Roach and Ghost.]]
* Possible in ''VideoGame/SpiderManWebOfShadows'' if you choose to let the Symbiote have its way. In the end of an all villain story, Spider-Man becomes the emperor of the Symbiotes and rules over New York City.
* In ''GuildWars'', [[spoiler:Vizier Khilbron, who appears about halfway through the Prophecies campaign, provides indispensable assistance to the players on several occasions in fighting the White Mantle and their Mursaat allies, and turns out to be the BigBad who has been manipulating the player all along to set up the proper conditions for his Titans to assault Tyria so he can take it over.]]
** The leaders of the White Mantle, and the White Mantle as a whole. The Bonus Mission Pack shows White Mantle founder Saul D'Alessio as a pretty swell guy, fearlessly defending his homeland from the Charr in an epic battle with help from the Mursaat. What did he get for his trouble? The Mursaat kidnap him and take him away forever as payment for their help. The remaining survivors, who felt understandably betrayed and ripped off, decided fighting for justice isn't all it's cracked up to be, and instead started a campaign to take over Kryta and secure absolute power for themselves.
** Shiro Tagachi. Granted he was manipulated into becoming corrupt and evil, but it's strongly implied that he used to be quite a fearsome defender of the innocent in his younger days.
** Torin, a rather unimportant Ascalon Guardsman in the beginning of the Prophecies campaign, becomes a bandit after the apocalyptic Searing event. A quest directs you to find him and his bandit comrades outside Fort Ranik and kill him. The reason for his face heel turn is never explained. Then again, he was the minor-est of minor characters to begin with, so it's probably not important to the storyline.
** More Ascalon Guards turn heel after the Searing: Footman Tate and Footman Quinn stole a priceless artifact from a temple and ran off with it. Their reasons are never explained, though it's probably simple greed. A quest has you hunting down the traitors. Footman Tate surrenders after a short dialogue, but Footman Quinn is hiding far from any civilized settlement and will attack you on sight without a word.
** Markis, the Shining Blade councilman from Prophecies. He initially appears as a high ranking Shining Blade officer with the group's best interests at heart. After a few conspicuous absences, it's later revealed that he's a White Mantle infiltrator. Late in the campaign, he taunts you about Saidra's death and your stupidity at falling for his ruse. It ends with the player's group getting a very well-deserved ''RoaringRampageOfRevenge'' on him.
** Elonbel from the Nightfall campaign. A local guardsman on Istan who cuts a deal with a local bandit group. When the player discovers his treason, he sides with the bandits and you're forced to kill them all. He's actually pretty tough, being a relatively high level enemy in a starting area of the game.
* In the wii flight game ''InnocentAces'' [[spoiler: Orishima does this after a mock battle with the player because she had so much fun that she wanted a rematch]].
* Something similar to Sophitia above happened in ''VideoGame/BlazBlueContinuumShift''. [[spoiler:By the end of the series, [[ChineseGirl Litchi Faye-Ling]] is [[ForcedIntoEvil forced to join the bad guys' side]], since the bad guys kept the lover she's been trying to cure (Arakune) as a hostage and they had the cure she badly wanted, and she has to join if she wants both the cure and that lover. Throughout the series, she's usually one of the genuinely good characters.]]
** Also, thanks to a case of LoveMakesYouCrazy and some mental manipulation from [[BigBad Hazama]], there's [[spoiler:[[LadyOfWar Tsubaki Yayoi]].]].
* Jan Kurtas/Medusa in ''VideoGame/{{Odium}}'' was a victim of ViralTransformation that turned him into a monster, but - unlike all other townspeople - he did not become an insane killing machine. Unless you blunder into the (entirely avoidable) scripted sequence where he finally succumbs and attacks you. (You can get an OptionalPartyMember as a replacement afterwards.)
* Nathan Hale in ''VideoGame/{{Resistance}} 2'' in the ending. Though only briefly.
* ''VideoGame/NieR'' has two examples.
** First, [[spoiler:the Twins, Popola and Devola are initially major allies in Nier's quest, but late in the game turn out to be two of the story's central villains.]]
** Secondly, [[spoiler:In the path to endings C and D (which is only possible by obtaining every weapon on a NewGamePlus), Kaine's Shade half takes full control over her, turning her into the FinalBoss.]]
* Dan Stewart in ''VideoGame/WinBack: Combat Operations''.
* ''VideoGame/DoubleDragon'', in which Billy and Jimmy fight side-by-side through everything to rescue the girl, only to find that Jimmy is indeed the BigBad.
* [[spoiler:Wheatley, after the core transfer with GLaDOS]] in VideoGame/{{Portal 2}}. In fact, the audio files for these lines have "heel turn" in their names.
* In the WebGame [[{{TCT RPG}} The Colour Tuesday,]] Paige tries to seize the [[ChekhovsGun guitar of Alex's disappeared brother]] when she tries to claim it.
* In NightTrap...[[spoiler:you, in the perfect ending. [[http://www.youtube.com/watch?v=HnVKqlyjz7s If you are so inclined.]]]]
** [[spoiler: You don't even go that fair. Just let one of the Martins escape during the final sequence and kick back and watch the fun. You get the same ending either way.]]
* SepterraCore. Selina, when [[spoiler: she saw Doskias almost getting killed by one of the good guys]]. Actually, she goes back and forth a few times throughout the game.
* Marty "Monk" Malone is a loyal Corleone enforcer and a good friend of the protagonist in the video game adaptation of ''VideoGame/TheGodfather''. When [[spoiler: his sister is murdered late in the game]] to get at the protagonist, Monk becomes embittered and eventually turns traitor, forcing the player to kill him.
* ''VideoGame/PokemonMysteryDungeon'' has this seemingly innocent line, if it wasn't for its [[DissonantSerenity dissonantly gleeful]] delivery:
--> '''[[spoiler: Your partner]]:''' ''"The world of darkness is going to be wonderful.''
* Clyde in ''{{Vigilante 8}}'' goes from a member of the Vigilantes opposing [[CorruptCorporateExecutive OMAR]] and their thugs to the CEO of OMAR who stole a time machine to kill his former leader and ensure the submission of the US in the sequel thanks to [[spoiler: finding [[BrainwashedAndCrazy Houston]]'s mind control bracelets in a service station bathroom.]]
* Quox, TheDragon of ''TheTowerOfDruaga'', was an ally of Ki in ''VideoGame/TheQuestOfKi'' who turned evil after Druaga split the Blue Crystal Rod.
* [[spoiler:Almalexia]] did this at some point prior to the ''Tribunal'' expansion to ''VideoGame/TheElderScrollsIIIMorrowind'', due in large part to loss of access to the Heart of Lorkhan.
* Both [[spoiler:Dr Sorkin and Yoder]] turned on the team for their selfishness in episode 4 of JurassicParkTheGame.
* Both [[spoiler:Jaesa Wilsaam]] and [[spoiler:Nomen Karr]] in ''Videogame/StarWarsTheOldRepublic'' did this the first to join you and the second to kill you...3 times
* In the second to last route of ''VideoGame/DuelSaviorDestiny'' [[spoiler:Selbium Volt]] turns on Taiga due to [[spoiler:first blaming him for Mia's 'death']] and when that turns out not to be the case he still blames him for ...something or other and gets even more antagonistic. [[spoiler:And despite Taiga attempting to show him mercy, he tries to stab him in the back after the DuelBoss fight and gets killed for his trouble.]]
* This isn't a trope that Starscream in TransformersWarForCybertron would go down as he's more related to TheStarScream, but he starts out as an Autobot Scientist at the beginning of the Decepticon campaign. After Megatron bests his defenses, Starscream switches from the Autobots to the Decepticons. He later pulls his own trope off.
* ''VideoGame/MortalKombatDeception'' sees Kabal actually ''reverting'' to his bad guy ways and ''running'' with it. After being rescued from death by the Chaos cleric Havik, Kabal is convinced to resurrect the criminal Black Dragon clan. He then finds Mavado (the Red Dragon thug who put him at Death's door), pays him back double, steals back his hookswords (which "feels good" for him to hold again) and then hires young, methodical killers to transform the Black Dragon from a band of pirates into a nihilistic organization determined to overthrow civilization. And Heaven help you if you don't fit Kabal's criteria of what a Black Dragon should be.
* In ''VideoGame/SlyCooperThievesInTime'', the villainous Black Knight terrorizing Medieval England is revealed to be [[spoiler: Penelope, a supporting character and ally in [[VideoGame/Sly3HonorAmongThieves the previous game]] and love interest of Bentley. She has gotten tired of Bentley "wasting" his brain power with the Cooper Gang, and gives her boyfriend's time machine plans to the BigBad in order to gain profit, kickstarting the entire plot of the game.]]
** Oddly enough, [[spoiler: her change from quirky LoveInterest to evil MadScientist was probably the strangest part of the story. Since there wasn't any ForeShadowing in the previous game that would lead to her becoming evil, it came off as clumsily executed. This is forgiven, however, because after all, if she didn't suddenly change sides, then we wouldn't have a game.]]
* Karnov has a do-it-yourself variation of the trope; He was the first boss in ''VideoGame/BadDudes'' and the final boss in ''VideoGame/FightersHistory''.
** Chelnov from ''Atomic Runner'' did this trope himself as the final boss of ''Fighters History: Mizoguchi Kiki Ippatsu''.
* In ''VideoGame/TheNightOfTheRabbit'' the BigBad [[spoiler:Great Zaroff]] and his mentor [[spoiler:Marquis de Hoto]] were heroes until some years prior the events of the game.
* Happens to [[spoiler: Salem]] in the 3rd game {{Army of Two}}: The Devil's Cartel, and he is also the final boss in the game.
* In ''VideoGame/FinalFantasyTacticsA2'' there's a pair of paladins who were known for the superb swordsmanship and skills in combat. However, one of the paladins, Frimelda, is superior to her other paladin friend, Luc Sardac, in battle skills. Luc Sardac tries his best to match his skills with Frimelda's, but he could never get any better. Rather than accepting his limitations, Luc Sardac decides to kill Frimelda so that he would be the superior paladin. It didn't stick due to Frimelda's sheer force of will keeping her alive, but as a zombie. When the zombified Frimelda and your party confront Luc Sardac over what happened, he decides to attack you.
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