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->''"Don't be a fool. The only one I ever loved was God. And that was a long time ago!"''
-->-- '''ArchangelLucifer''', ''Series/{{Brimstone}}''

So you have your EccentricMentor and with his backing you're facing off against the nefarious machinations of the local EvilSorcerer, when suddenly you learn a shocking truth -- in their youth, rather than being bitter enemies, these guys were best friends!

This trope occurs whenever a good aligned character (sometimes TheHero, but more commonly TheMentor, the SupportingLeader, or the BigGood) is revealed to have had a history as friend, ally, mentor, or even student with a major villain (commonly the BigBad, but sometimes TheDragon or another high-ranking [[EvilMinions Evil Minion]]). Usually the friendship fell through simply because the future villain went power-mad and the other character didn't want any more to do with it, but more complex and unusual variations exist. Sometimes it will be known all along, but sometimes it will be the subject of a dramatic reveal that can lead TheHero and the audience to reevaluate what they know about both characters.

As the top of the page indicates, tends to happen a disproportionate amount of the time with the resident [[EccentricMentor Wise Old Wizard]] and the EvilSorcerer. Compare and contrast BigBadFriend, where the revelation occurs during the story and the "Bad" character was evil all along (or at least had been for a while) and would rather remain friends despite this. Usually, either the evil character will be a FallenHero or the good one will be TheAtoner (or both, if both started out more morally grey). The evil character will most likely be an EvilCounterpart and/or ShadowArchetype for the good one, and may also be their ArchEnemy. If traces of the past friendship still exist, they might be FriendlyEnemies or even have FoeYay. Compare and contrast RivalTurnedEvil, for where the friendship broke up over personal rivalry before one of the characters turned evil (though certain examples will overlap, not all will). A less extreme version of the falling-out is WeUsedToBeFriends.

Note that this is about friends who turned evil in the {{Backstory}} and are either introduced or established in their first appearance as villains. If the friend turns evil over the course of the work, see FaceHeelTurn. See WeUsedToBeFriends when characters are friends but then something breaks them apart.



[[folder:Anime & Manga]]
* ''Manga/{{Naruto}}'':
** Jiraiya, Tsunade and Orochimaru were once on the same squad. Jiraiya was Orochimaru's closest friend, before Orochimaru abandoned the Leaf Village. Jiraiya chased him down and tried to talk him out of it, but Orochimaru laughed in his face.
** Kazuma of the 12 Guardian Ninjas filler arc was one to Asuma, as they served together in the Guardian Ninjas until Kazuma betrayed the group with five of his comrades to pursue their extremist agenda of making the daimyo the sole authority of the nation.
** Tobi has been revealed to be Obito Uchiha, Kakashi's best friend and role model. The pain of this revelation left Kakashi reeling in shock long enough to nearly be killed.
** And of course there's Sasuke, [[ChronicBackstabbingDisorder who betrayed Konoha and Naruto to follow in Orochimaru's footsteps only to betray him, too, join the Akatsuki, and then betray them, all the while forming his own faction. A member of which he tried to kill after abandoning the others]].
*** This hearkens back to his own relationship with Itachi. Sasuke absolutely adored his older brother, only for said brother to murder their entire clan. His conflicting love for his brother and hate for what he had done were eventually used by Tobi to manipulate him.
** [[spoiler:Madara Uchiha and Hashirama Senju]] were good friends despite the intense rivalry between their clans, enough that after years of war they were able to work together to [[spoiler:found Konoha]]. Despite this, the mistrust of [[spoiler:Hashirama's brother]] eventually convinced [[spoiler:Madara to turn his back on Konoha and become the BigBad]].
* ''Manga/SoulEater'''s [[TheGrimReaper Shinigami]] and [[HumanoidAbomination Asura]].
* Yuka Sugimoto is this to Youko Nakajima in ''LightNovel/TheTwelveKingdoms'', sort of. [[spoiler: She gets better once defeated, tho.]]
** In different degrees, also [[spoiler: Youko and Yuka's boyfriend Asano. He ''is'' closer to Youko than Yuka is, having known the future Queen of Kei from childhood.]]
* Enchu was formerly close friends with [[Manga/MuhyoAndRoji Muhyo]] and Yoichi, but turned to evil after his mother died and Muhyo became an executor instead of him, and serves as the main antagonist for much of the story.
* Toguro toward Genkai in ''Manga/YuYuHakusho''.
* [[GeneralRipper Regius]] for Zest in ''Anime/MagicalGirlLyricalNanohaStrikers''. The two used to be friends while serving together in the bureau, and wanted to ensure that the Bureau's ground forces were able to deal with criminals and other threats. Over time, Regius lost sight of his ideals as he fell under the sway of the High Council, and eventually [[spoiler:Zest and nearly all his team were killed on a raid on a Combat Cyborg facility]]. Zest, [[spoiler:after being cloned]], sought out Regius for answers on why he changed, [[spoiler:but Due killed Regius before he could give any]].
* In ''Manga/FushigiYuugi'', Miaka and Yui are both best friends until the two are pitted against each other. The odd thing about this particular example is that Yui is deceived into thinking Miaka is the one who turned against her, and that she, not Yui, is the one who is turning evil.
* In ''Anime/SuitePrettyCure'', [[CatsAreMean Siren]] and [[CuteKitten Hummy]] used to be the best of friends until Hummy took Siren's title as singer of the annual "Melody of Happiness", causing the latter to defect to the villains' side. They ''almost'' made up early in the series before [[BigBad Mephisto]] [[BrainwashedAndCrazy forcefully won Siren's loyalty back]]. However, they do get a proper reconcilliation about nine episodes later, leading to Siren joining the team as [[SixthRanger Cure Beat]].
* Who else but Guts and Griffith of ''{{Manga/Berserk}}''? The two men had a bond bordering on brotherhood (or if you're that way inclined, [[HoYay more than that]]), only for Griffith to turn his back on him and everyone else he led during the events of the Eclipse, which would destroy this bond forever and leave Guts with an undying hatred for Griffith.
* In ''Manga/{{Akira}}'', Tetsuo is this to Kaneda. Both have been friends since their first meeting in an orphanage.
* ''Manga/KenichiTheMightiestDisciple'': [[spoiler:Odin a.k.a. Ryuto Asamiya]] used to be friends with the titular character before a fight that led to him holding a years-long grudge. He's also a ForgottenChildhoodFriend, as Kenichi initially didn't recognize him in the present day.
* Shin used to be Kenshiro's best friend in ''Manga/FistOfTheNorthStar'' up until he was manipulated by Kenshiro's evil brother Jagi into turning against him and taking Yuria, who both Kenshiro and Shin loved, for himself.
* In ''Manga/RaveMaster'', Gale Raregroove, aka King the leader of Demon Card, and Gale Glory, Haru's father, used to be the best of friends. A huge helping of tragedy and poor decisions made them bitter enemies. The worst part is that it's implied near the end of the series that this was partly due to fate constantly screwing over the Raregroove bloodline.
* In ''Anime/CuteHighEarthDefenseClubLove'', Kinshirou is this to Atsushi. They were very close up until middle school, and despite his yen for world domination, Kinshirou is ''still pining'', throughout the closing titles, Episode 4, and most of the rest of the series. [[spoiler:But all ends well]].

[[folder:Comic Books]]
* Professor X and ComicBook/{{Magneto}} in most versions of the ''Franchise/XMen''.
** ComicBook/{{Wolverine}} and ComicBook/{{Sabretooth}}. ''First X-Men'' actually shows us why the two went their separate ways. After forming a group of mutant rebels to fight the government, Victor wants to take off with his love interest and leave the fighting to someone else. However, Wolverine, by that point, had already convinced everyone that what they were doing was necessary, so she stayed. She is killed in the final conflict, but instead shows Victor a vision of her getting better, and the two having a family and living a happy life, before cutting the illusion and telling Creed ''that'' is what he should remember, and that it doesn't have to mean anything less. Creed took this to heart, blaming Logan for taking away his happy ending, and told Logan that he would ensure that he never find anything or anyone worth living for.
* Franchise/{{Superman}} and ComicBook/LexLuthor, in [[UsefulNotes/TheSilverAgeOfComicBooks some]] [[Series/{{Smallville}} versions.]]
* [[ComicBook/TwoFace Harvey Dent]] is shown as a close friend of both Franchise/{{Batman}} and Commissioner Gordon before turning into Two-Face, particularly in ''ComicBook/TheLongHalloween''.
** Black Mask and Hush were both Bruce Wayne's childhood friends, having turned into supervillains in their adult lives.
* Apparently Megatron and Optimus were this in the [[ComicBook/TheTransformersIDW IDW]] continuity and in the Movie prequel comics and [[Comic/TheTransformers Marvel UK annuals]] as well.
* On Tatooine, Luke Skywalker only had two friends who shared his desire to go offworld, and both, being older than him, joined the Imperial military before ''Film/ANewHope''. Biggs Darklighter became a pilot, [[DefectorFromDecadence defected]] to the Rebellion, and [[MauveShirt died at Yavin]]. Luke's other friend, Janek "Tank" Sunber, was shown [[Franchise/StarWarsExpandedUniverse in the comics]]; he washed out of pilot training and became an infantry officer. Of course, he came into conflict with Luke.
* In the ComicBook/{{New 52}}, ComicBook/{{Nightwing}}'s newest foe Saiko [[spoiler:is former friend and fellow former member of Haly's circus Raymond. Raymond was taken by the Court of Owls and put through TrainingFromHell to become a Talon, only to be washed out and left for dead with his eyes pecked out by birds.]] Saiko hates Dick Grayson because [[spoiler:the Court only took Raymond because they couldn't get Dick, their original candidate, after Bruce Wayne adopted him in the wake of the Flying Graysons' deaths.]]
* At first played straight but then subverted with the ComicBook/{{New 52}} version of ComicBook/TheCheetah. Franchise/WonderWoman tells the JLA that Barbara Minerva was her first true friend in Man's World, a scholar who helped Diana on various quests for mystical artifacts. Studying a dagger, Barbara was cut by it and transformed into the Cheetah. She and Diana fought numerous times, with Diana trying to help her friend and considering her a victim. However, meeting the cult who created the dagger, Wonder Woman learns that the Cheetah is meant to be a protecting spirit but the inner darkness within Barbara turned it into a beast. Batman then reveals that "Barbara Minerva" was the alias of a long-time thief, con artist and attempted murderer and Diana is rocked to realize that Barbara was never an innocent or her friend.
-->'''Batman''': The Cheetah never corrupted Barbara. Barbara corrupted the Cheetah.
* [[ComicBook/FantasticFour Reed Richards]] and Doctor Doom were college students who could only find intellectual debate and stimulation from each other, until Reed pointed out a mistake in Victor's schematics which was part of his last step in his StartOfDarkness.
* In ''ComicBook/TheFlash'', there's Hunter Zolomon, formerly a close FriendOnTheForce to Wally West, before Gorilla Grodd broke his back and set the stage for him to become [[EvilCounterpart Zoom]].
* In ''ComicBook/ConanTheBarbarian'' Thoth Amon is revealed to have been Kalanthes's best friend at one point before he turned to Set worship and destroyed everything Kalanthes holds dear. Even before that was revealed there were hints that their hatred went deeper than religious differences.
* ''ComicBook/MyFriendDahmer'' is all about the narrator being classmates and friends with [[SerialKiller Jeffrey Dahmer]], though he states he always felt like ''something'' was off. He had no idea just how right he was, but it was enough to keep him at arm's length, hanging out with Dahmer at school but not wanting to get any closer than that.

[[folder:Fan Works]]
* In ''Fanfic/FriendshipIsMagicalGirls'', Lightning Dust is this to Rainbow Dash. They used to be close friends when they were younger, but after Lightning moved away, she fell into a life of crime, eventually becoming a member of the Shadowbolts by the time she and Rainbow re-encounter each other. And while Rainbow is [[BigBadFriend currently unaware of this]], she is aware that Lightning is thieving {{Jerkass}}, while Lightning knows perfectly well that Rainbow is one of heroes she's fighting, and doesn't seem to care.
* In ''FanFic/WhyAmICrying'' showed that Apple Bloom and Diamond Tiara were best friends as foals. Diamond moved to Manehattan when she was four, and then moved back to Ponyville three years later after suffering from a series of hardships (like losing her mother and going through Tartarus at corrupt summer camp). When she did, she found that [[StrangerInAFamiliarLand none of her old friends remembered her]], not even Apple Bloom. It was Apple Bloom [[EtTuBrute chewing her out for "bullying" her new friends]] (when in fact, ''they'' were the ones who started the fight) that proved to be [[RageBreakingPoint the final straw]] for Diamond, who sought to ruin her life since.

[[folder:Films -- Animation]]
* ''WesternAnimation/ToyStory3'': [[spoiler: Lotso]] was this to Chuckles the Clown. Witnessing [[spoiler: Lotso]] become a monster resulted in Chuckles becoming bitter and cynical.

[[folder:Films -- Live-Action]]
* ''Franchise/StarWars'':
** Darth Vader and Obi-Wan are a double-hitter, as Vader (as Anakin Skywalker) was both Obi-Wan's student and his closest friend.
** Count Dooku was also once a respected Jedi Master who got on well with his former teacher Yoda and peer Mace Windu. In this case the revelation, especially to the characters, was the fact that he'd turned evil rather than that he had been someone's friend.
* Alec Trevelyan to Film/JamesBond himself in ''Film/GoldenEye''.
* It's a plot-point in ''Film/{{Unbreakable}}'', and the last spoken lines in the film are the evil former friend specifically talking about it as a trope in fiction.
* TheDragon Maxim Horvath is this to Balthazar Blake in ''Film/TheSorcerersApprentice''. Also a case of LoveMakesYouEvil, as he became evil after Veronica Gorloisen rejected him in favor of Balthazar.
* Staci Blake from ''Film/{{Sleepover}}'' is a less intense version of this. Julie talks about how she and Staci used to be friends before joining the popular clique. Despite her former friendship with Julie, Staci continuously insults Julie and her friends and even sabotages their chances of winning.
* Steve Rogers and [[spoiler:Bucky Barnes/Winter Soldier]] in ''Film/CaptainAmericaTheWinterSoldier'' [[spoiler:although how 'evil' the latter can be considered is up for debate.]].
** Also Nick Fury and BigBad [[spoiler: Alexander Pierce]].
* ''Film/XMen'':
** Naturally while Magneto remains on FriendlyEnemy terms with Charles Xavier, the X-Men and Brotherhood are at great conflict in the majority of films regardless.
** Pyro to Bobby.
* Hector Barbossa is Jack Sparrow's Evil Former First Mate in ''Film/PiratesOfTheCaribbeanTheCurseOfTheBlackPearl''. In the third movie [[spoiler:the fact [[WeUsedToBeFriends they used to be friends]] is played up much more, and by the fourth they're VitriolicBestBuds again.]]
* Doom is presented as former friend of the ComicBook/FantasticFour in most live-action film encarnations like ''Film/FantasticFour2005'' and ''Film/FantasticFour2015''.

* In ''Literature/ABrothersPrice'', there is [[spoiler: Kij Porter, although she may never have had actual friendly feelings for Ren.]] After the evilness is exposed, [[spoiler: Ren decides they aren't friends anymore, too.]]
* Several times in ''Literature/HarryPotter'' -- Albus Dumbledore and Gellert Grindelwald were best friends (and [[HoYay a bit more]], at least on Albus's end). Later on, Tom Riddle, the future Lord Voldemort, was Dumbledore's student, and at least one of the Sorting Hat's songs implies that Godric Gryffindor and Salazar Slytherin were once good friends as well.
** Subverted with Sirius Black, who looks like the evil part of this in comparison to Harry's dad, but is revealed to have been framed. Played straight with Peter Pettigrew, another former friend who ''was'' guilty and did the framing.
** As well as [[spoiler:Lily Evans and Severus Snape]], until the latter's HeelFaceTurn.
* Gandalf and Saruman from ''Literature/TheLordOfTheRings'' have elements of this, though their relationship doesn't shatter until early in the present storyline (though the books at least show that it had been fraying for a while before that because of Saruman's jealousy).
** They had never been exactly good buddies; according to the [[AllThereInTheManual Appendix]] Saruman had been jealous of Gandalf almost as soon as they stepped off the ship in the Gray Havens, but they had had mutual respect and a common purpose.
* [[EvilSorcerer Akhlaur]] and [[ReasonableAuthorityFigure King Zalathorm]] from ''Literature/CounselorsAndKings'' were once best friends, until Akhlaur proved that WithGreatPowerComesGreatInsanity.
* ''Literature/{{Warbreaker}}'' has Vasher and Denth as an interesting variation [[spoiler: because the friendship ended violently over something ''Vasher'', the good guy of the two did. They were originally part of the same group of famous magic-users, and Vasher killed Denth's sister, another member, fearing that her knowledge of how to create Artifacts of Doom would spread. Denth went on a RoaringRampageOfRevenge to avenge her, gradually descending into evil in the process.]]
* In ''Literature/TheDeathGateCycle'', [[WellIntentionedExtremist Samah]] and [[EccentricMentor Zifnab]] were at least cordial colleagues and possibly friends, at least until Samah went all KnightTemplar and Zifnab dedicated himself to opposing him.
* Though calling them "friends" would be a stretch (he was never a particularly ''nice'' guy), Zedar from ''Literature/TheBelgariad'' was once a Disciple of Aldur along with the EccentricMentor Belgarath, and the two worked closely together and respected each other. Then [[BigBad Torak]] {{Mind Rape}}d Zedar into becoming TheDragon, and it went rapidly downhill from there.
* From ''Literature/TheSagaOfDarrenShan'' [[spoiler: Darren's former best friend, Steve]].
* From ''Literature/TheElenium'', comparatively rare example of the main hero having a prominent villain as one of these- Martel and Sparhawk were good friends who went through MagicKnight training together, until Martel got caught practicing BlackMagic and was expelled from the order. Though now enemies, they're still very polite to each other and respect each other's abilities, and conduct their final duel in a most gentlemanly manner.
** From ''Literature/TheTamuli'', Sephrenia and Zalasta had been friends from childhood, and Styric lifespans are very long. It didn't end well. [[spoiler:Unfortunately for everyone, Zalasta was driven by a very extreme case of LoveMakesYouEvil.]]
* Alan Garner's ''Literature/TheWeirdstoneOfBrisingamen'' ends with a fight between Cadellin and Grimnir, the evil wizard. When [[spoiler: Cadellin kills Grimnir, he reveals that they were once friends [[CainAndAbel and brothers]].]]
* In ''Literature/MemoirsOfAGeisha'', Sayuri and Pumpkin, who started out as friends, but once [[spoiler: Mother adopted Sayuri instead of Pumpkin and she became a more popular geisha than Pumpkin]], they became rivals (at least in Pumpkin's mind).
* In ''Literature/PercyJacksonAndTheOlympians'', Luke was this to Annabeth and Thalia.
* De Quincey to Camille in ''Literature/TheInfernalDevices''. Apparently he still doesn't get the message that she doesn't see him as a friend - or anything else, for that matter - anymore, [[spoiler: not after he killed her werewolf lover.]]
* In ''Literature/PrideAndPrejudice,'' Mr. Darcy and Mr. Wickham were childhood friends until they grew up and the latter revealed his selfish, hedonistic, amoral character.
* In ''Literature/{{Updraft}}'', from Nat's perspective, the protagonist herself is this, due to seemingly aligning with the Singers despite knowing what they did to Nat's father. However, the two eventually accept that they were actually seeking the same basic thing by different routes, and reconcile.
* In ''Literature/TheWitchlands'', Serrit Linday used to be Vivia's best friend before he decided to align himself with [[spoiler:the Big Bad]] for his own profit.

[[folder:Live-Action TV]]
* Oliver and [[spoiler:Slade Wilson/Deathstroke]] on ''Series/{{Arrow}}''.
* Giles and Ethan from ''Series/BuffyTheVampireSlayer''
-->'''Ethan:''' Oh, so cross Ripper. We used to be friends. When did all that fall apart?\\
'''Giles:''' About the same time you started to worship chaos.\\
'''Ethan:''' Oh. Religious intolerance. Sad, that. I mean, just look at [[UsefulNotes/TheTroubles the Irish Troubles]].
* ''Series/BurnNotice'' has Michael Westen's former partner-in-spying Larry Sizemore, who becomes a PsychoForHire after he faked his death in Serbia. He shows up in Miami running a sort of freelance assassination business; he shows up in a few episodes, during which he forces Michael into Enemy Mine situations.
* The Doctor and the Master, from ''Series/DoctorWho''. They're still sort of FriendlyEnemies, but when they were schoolkids together, they weren't enemies at all, and the Doctor has some serious angst about this.
-->''"Do you remember my fatherís land back home? Pastures of red grass, stretching far across the slopes of Mount Perdition.'' ''[[MeadowRun We used to run across those fields all day,]]'' ''[[HoYay calling up at the sky...]]'' ''[[FoeYay Look at us now."]]''
** The Twelfth Doctor gives this beautiful summary in "Death In Heaven":
--> ''I had a friend once. We ran together when I was little and I thought we were the same. When we grew up, we werenít. And now sheís trying to tear the world apart and I canít run fast enough to hold it together.''
* ''Series/GameOfThrones'': Theon Greyjoy to Robb Stark. After Eddard Stark's execution in King's Landing, Theon pledges his loyalty to Eddard's eldest son, Robb, in the subsequent War of the Five Kings, but ultimately betrays Robb and sides with his father in invading the North.
* ''Series/HouseOfAnubis''. For Sarah Frobisher-Smythe, both Victor Rodenmaar and Rufus Zeno fit this trope. Victor and Rufus, being the two major villains of season 1 and both major again in season 2, as well as both antagonizing Sarah for a secret she doesn't have, were both once Sarah's childhood friends and eventually business partners, until they both became corrupted with power and greed and turned on her, and each other as well.
* On ''Series/{{Justified}}'' US Marshal Raylan Givens and local criminal Boyd Crowder grew up in the same community and then 'dug coal together' in the local coal mine. The show starts when Raylan is forced to return to Kentucky and has to confront Boyd who in the meantime became the leader of a Neo-Nazi gang of bank robbers.
* Regina to Snow White on ''Series/OnceUponATime.'' It's played for a fair amount of tragedy too. There are a number of scenes devoted to showing how Regina changed from a kind, caring young girl to a vicious [[EvilSorcerer Evil Sorceress]].
* Played with a bit sideways in ''Series/StargateAtlantis''. Lt. Ford starts out as a member of the team and friend to Col. Shepard, but in the 1st season finale he gets overdosed with a wrath drug and goes off the deep end. He doesn't see himself as evil, but his actions in the episodes where he makes his returns are... less than friendly. Including kidnapping Shepard's team and pumping them full of the same drug against their will.
* ''Series/TheNewAvengers'': In "Dead Men Are Dangerous", Steed's life is threatened by a revenge campaign from Mark Crayford, a childhood friend (at least to Steed), who viewed Steed as a lifelong rival, and who Steed was forced to shoot when he revealed himself to be a double agent.

* The music of Music/TheMegas, being based on the "VideoGame/MegaMan" series, retains this dynamic between Doctor Light and Doctor Wily, and it's made the war they've found themselves waging against each other very personal.

[[folder: Myths & Religion]]
* In Myth/NorseMythology, Odin and Loki were once [[BloodBrothers sworn brothers]].
* Many tellings of the {{Satan}} story will have pre-Fall Lucifer as God's favorite angel. In some, he was Archangel Micheal's closest friend.

[[folder:Pro Wrestling]]
* In Wrestling/{{Progress Wrestling}} Jimmy Havoc is this to Zack Sabre Jr and Paul Robinson is this to Will Ospreay.

* Delia Ketchum used to date Giovanni in the ''Theatre/PokemonLive'' musical. In an original draft of the show, Giovanni was Ash's father.
* ''Theatre/{{Wicked}}'' has an interesting take on this (and this is true for the novel as well): although neither Elphaba nor Glinda is truly a villain in the novel at hand, its entire premise is that it functions as backstory to the original ''Film/TheWizardOfOz''. If one were to take ''Wicked'' as behind-the-scenes canon for ''Wizard'', Elphaba's and Glinda's relationship -- as friends in the former and on opposite sides of the conflict in the latter -- would certainly qualify.

* ''Toys/{{Bionicle}}'': Vakama's mentor, Toa Lhiikan, had not one but two of his teammates who went bad, both of whom later returned to menace later heroes.
** Toa Tuyet, who was willing to murder several Matoran and pin it on the Dark Hunters just to cover up the fact that she was hiding a powerful aritfact, and tried to use said artifact to take over the city after she got caught. She was taken away by the Order of Mata Nui in secret, but later escaped.
** Toa Nidhiki, not that you'd know it by his current insectoid appearance. He tried to sell out the Toa to the Dark Hunters in return for being put in charge of the conquered city, but Lhiikan overheard him making the plans and set a trap of his own, and forced Nidhiki to leave with the defeated Hunters. When he tried to betray ''them'', The Shadowed One hired [[FemmeFatale Roodaka]] to use her powers to transform him into his current state ([[AndIMustScream the irony being that]] [[IronicHell he's ''terrified'' of insects]]).
* In LEGO's ''WesternAnimation/LegendsOfChima'' line, the main protagonist Laval of the lion tribe used to be friends with Cragger of the crocodile tribe before the latter got a taste of [[SuperSerum Chi]] and inadvertantly started the war that the story revolves around. Similarly, he was friends with Worriz of the wolf tribe before they allied themselves with the crocs under Cragger's leadership.

[[folder:Video Games]]
* [[PlayerCharacter Chell]] and [[IdiotBall Wheatley]] had more of a hero/sidekick relationship at the start of ''Videogame/Portal2'', but they were still very close (or at least as close as a [[MotorMouth talkative]] [[RobotBuddy robotic eyeball]] and a [[RunningGag potentially braindamaged]] [[HeroicMime mute]] can be). This changes when [[spoiler: Wheatley [[FaceHeelTurn turns on]] Chell half-way through the game, taking the title of BigBad from [=GLaDOS=] and serving as the FinalBoss]]. Later dialogue confirms that Wheatley did see Chell as a friend before [[spoiler: his FaceHeelTurn]].
-->'''Wheatley:''' Aw. Just thinking back to the old days, when we were friends. Good old friends. Not enemies. And I'd say something like 'come back', and you'd be like 'no problem!' And you'd come back. What happened to those days?
* Athos and Nergal from ''VideoGame/FireEmblem''.
* ''Franchise/AceAttorney'':
** Phoenix Wright and Miles Edgeworth in ''Phoenix Wright: Ace Attorney''. They had a brief but close friendship as children, until Edgeworth's father was murdered and he was taken in and raised to be a ruthless prosecutor by Manfred von Karma. When Phoenix saw what his old friend was becoming, he studied to become a defense attorney just to face him in court. Their reunion was.... bitter, but [[BreakTheHaughty ultimately]] Edgeworth [[HeelFaceTurn turned himself around]] and [[CharacterDevelopment became an honest prosecutor]] who didn't care if he 'won' as long as the truth came out -- all because Phoenix refused to give up on their friendship.
** Case 1-5 has this with Lana Skye and her old co-workers, Angel Starr and Jake Marshall. They all worked together to catch the serial killer Joe Darke, but then Lana grew cold and distant and rumors began to fly that she was using less-than-legitimate methods to catch criminals. [[spoiler:As it turns out, she was being blackmailed.]] This is also implied to be the case between the Judge and [[spoiler:Damon Gant]].
** Subverted in ''Dual Destinies'', with [[spoiler:Athena and Simon]]. While they had once been friends [[spoiler:when Simon worked with Athena's mother, and apparently ended up killing her,]] it's revealed that [[spoiler:not only was Simon not the murderer, Athena never believed he was and has spent her life trying to prove it.]]
* Dr. Light and Dr. Wily had this relationship in ''VideoGame/MegaMan''.
* Porky and Ness in ''VideoGame/EarthBound'' were likely once close friends. [[spoiler: [[FightingYourFriend Until things went horrendously out of control]].]]
* Revan and Malak in ''VideoGame/KnightsOfTheOldRepublic''. Inverted in that it's common knowledge that they used to be friends; the twist is that Revan is still alive and back with the Jedi. During their final confrontation, a redeemed Revan can even apologise for leading their friend down the path to the Dark Side, but note that it was ultimately Malak's decision to continue down that path.
* The lead signature characters of ''VideoGame/CityOfHeroes'' and ''City of Villains'', Statesman and Lord Recluse, respectively, were best friends before Recluse joined Arachnos.
* [[Anime/CodeGeass Kallen Kozuki]] and [[Anime/MobileSuitGundam00 Louise Halevy]] in ''VideoGame/{{Super Robot Wars Z}}2''. [[http://www.youtube.com/watch?v=DZdwkxjT6r4 Louise calls out Kallen for working with ZEXIS]], even though Louise works for the A-LAWS.
-->'''Louise''': Kallen! You deceived me!
* Pigma Dengar was on the original VideoGame/StarFox team before his betrayal.
* In ''VideoGame/TransformersWarForCybertron'' it's taken it UpToEleven, with Optimus being swayed to help start Megatron's rebellion, and even successfully lobbying for the Council to grant the rebels an audience... where Optimus argued his understanding of ''Megatron's'' cause so well, the Council agreed and named Optimus the next Prime. Megatron saw this as a betrayal, and started the civil war, anyway. NiceJobBreakingItHero, indeed.
* "Arthur," in the UsefulNotes/SegaGenesis version of ''VideoGame/{{Ghostbusters 1990}}'', to the Weapons Shop owner.
--> "Did Arthur die? Once he was my friend. After he found the stone tablet he changed, but a long time ago he was a good man. To restore his good name, I'll repay you for your costs."
* ''VideoGame/Persona3'''s backstory has strong shades of this. Nearly everyone in the know about the Dark Hour (outside of about half your party) used to work together for the Kirijo Group's "Ergo Division" that researched Personas and Shadows, or were involved in their initial researches. Not all of them may have been ''friends'', as such (Strega has a very understandable grudge against Kirijo), but there are a lot of old professional relationships gone sour due to [[spoiler:Mitsuru's grandfather]]'s megalomania and the disasters it caused (and continues to cause).
* Two examples from the ''VideoGame/SlyCooper'' series:
** Dr M., the BigBad of ''VideoGame/Sly3HonorAmongThieves'' was a former member of the Cooper Gang when Sly's father was running the show and left the group after a falling out with Cooper Sr. He was TheSmartGuy to the group but hated the lack of recognition for his efforts, vowing to plunder the Cooper safe in revenge. He even attempts to invoke a FaceHeelTurn in Bentley for the same reason with a HannibalLecture [[spoiler: although Bentley is having [[ShutUpHannibal none of it]]]].
** [[spoiler: Penelope]] in ''VideoGame/SlyCooperThievesInTime'' betrayed the gang and [[spoiler: stole Bentley's time machine designs and sold them to [[BigBad LeParadox]]]] for the same reason as Dr M., apparently being convinced by his BreakingSpeech. [[spoiler: When Bentley, her boyfriend, found out he went into a serious HeroicBSOD.]]
* In ''Franchise/TheElderScrolls'' series' backstory, seen most prominently in ''[[VideoGame/TheElderScrollsIIIMorrowind Morrowind]]'', the [[OurElvesAreBetter Chimer]] and [[OurDwarvesAreDifferent Dwemer]] people of Morrowind were ancient enemies. When Morrowind was invaded by the [[HornyVikings Nords]], the Chimer and Dwemer formed an EnemyMine to drive the invaders out. During this time, the Chimeri leader Lord Nerevar and the Dwemeri leader Dumac became FireForgedFriends. Their people prospered under this alliance, with Dumac attending Nerevar's wedding and the two of them even attending the coronation of Emperor Gorieus representing their combined nation (Resdayn). However, the Dwemer Chief Tonal Architect, Lord Kagrenac, had discovered the [[CosmicKeystone Heart of Lorkhan]] beneath Red Mountain, and planned to tap into its power. Nerevar's advisor, Voryn Dagoth, convinced Nerevar that Dumac had become evil. Nerevar confronted Dumac, who demanded that Nerevar leave or be killed for questioning the motives of the Dwemer. This led to the [[GreatOffscreenWar Battle of Red Mountain]] and, as with [[TheRashomon many details surrounding that event]], the truth is likely lost to history.

[[folder:Web Original]]
* ''WebAnimation/{{RWBY}}'': [[AloofDarkHairedGirl Blake]]'s former parter/mentor [[KnightTemplar Adam Taurus]], who she claims was a good man before JumpingOffTheSlipperySlope. When they meet again, he is ''[[RevengeByProxy not]]'' [[RoaringRampageOfRevenge happy with her]] for [[DefectorFromDecadence deserting]] the [[YourTerroristsAreOurFreedomFighters White Fang]]. WordOfGod confirmed that the relationship was abusive even before that however.
* In one story in the ''Literature/WhateleyUniverse'', Phase muses on how a lot of the time, villains started off as the hero's best friend, and wonders if one day he'll end up enemies with his friends Mal and Jadis, who are the children of supervillains (Mal wants to be a villain and Jadis hasn't said whether she wants to be a hero or not, though the answer is probably yes).
* Anyone who has played ''Franchise/MortalKombat'' will know of the rivalry between Hanzo Hasashi (Scorpion) and Bi-Han (Sub-Zero), stemming from [[spoiler:EvilSorcerer Quan Chi disguising himself as Bi-Han and murdering Hanzo's entire clan and family]]. However, in the second season of ''WebVideo/MortalKombatLegacy'', we find out that they were childhood friends, despite their parents forbidding them from playing together due to the rivalry between their ninja clans. In fact, after they become the leaders of their respective clans, they declare peace, and Bi-Han is even willing to keep the peace after [[spoiler:Hanzo is forced to kill Bi-Han's brother while protecting his family]]. Shortly after that, [[spoiler:Hanzo and the the entire Shirai Ryu clan are slaughtered, apparently by Bi-Han and his Lin Kuei ninja. When Bi-Han finds out, he is ready to execute his lieutenants on the spot for this until he finds out that they weren't responsible]]. After Hanzo becomes the undead Scorpion and joins the Mortal Kombat tournament on the side of the [[TheEmpire Netherrealm]], he faces Bi-Han in combat. [[spoiler:Bi-Han's attempts to reach his childhood friend fall on deaf ears, and Hanzo ends up killing him in a gruesome way]].

[[folder:Western Animation]]
* Happens in several branches of the ''Franchise/DCAnimatedUniverse'':
** In ''WesternAnimation/BatmanTheAnimatedSeries'', Harvey Dent starts off as a close friend of Bruce Wayne before he becomes Two-Face.
** Terry [=McGinnis=] also received this treatment when his old friend fell back into crime and became Big Time in ''WesternAnimation/BatmanBeyond''.
** One that happened in ''WesternAnimation/SupermanTheAnimatedSeries'' but which didn't pay off until ''[[WesternAnimation/JusticeLeague Justice League Unlimited]]'' was [[spoiler: Professor Hamilton, who proclaims his eyes were [[SelectiveObliviousness "opened to the true danger of Superman"]] by his being driven BrainwashedAndCrazy by Darkseid and his angry outburst over Hamilton's refusing to help save Superman's dying cousin Supergirl. As a result, he joins up with the self-righteous {{hypocrite}}s of Project Cadmus, engaging in multiple morally dubious ''at best'' experiments to have a way to defeat the Justice League]].
* Fire Lord Sozin, the guy who started the War and the tradition of Fire Lords being [[EvilOverlord Evil Overlords]], was once best friends with Avatar Roku on ''WesternAnimation/AvatarTheLastAirbender'', though in a variation both characters are long dead by the time the viewer learns the details of their history.
* Vlad Masters from ''WesternAnimation/DannyPhantom'' was Danny's parents' best friend in college, until a botched experiment dreamed up by Danny's dad Jack (temporarily) disfigured him (and gave him superpowers, but he didn't find that out until later). Vlad is now dedicated towards three goals- killing Jack, convincing Maddie (Danny's mom) to fall in love with him, and making Danny his apprentice. Ironically, [[GeniusDitz Jack]] is the only one ''completely'' oblivious to all this. [[spoiler: At least until the GrandFinale]]
** In an episode where Danny tries to stop the accident that turned Vlad into a ghost, it was shown that Vlad was ''already'' jealous of Jack and his relationship with Maddie, and implies he would have still sought out Maddie even without ghost powers.
* Plankton to Mr. Krabs in ''WesternAnimation/SpongebobSquarepants''.
* ''WesternAnimation/TheBatman'' gives us Ethan Bennett, both a high-school friend of Bruce Wayne's and one of the only cops willing to give Batman a chance. [[spoiler:Naturally, he's accidentally turned into Clayface in the Season 1 finale. He eventually becomes a good guy again after spending a while in the HeelFaceRevolvingDoor.]]
* The Shredder had this relationship with the Ninja Tribunal in the second ''[[WesternAnimation/TeenageMutantNinjaTurtles2003 Teenage Mutant Ninja Turtles]]'' series.
** In one episode of the same series, Michelangelo ends up in a parallel universe where the Turtles are superheroes instead of ninjas. When he asks where their Splinter is, they say that they "lost him". The phrasing and their tone of voice causes Mikey to think that he's dead, but what they really meant was that they had lost him to evil, and he became their BigBad.
* In season 3 of ''WesternAnimation/XiaolinShowdown'', we discover that Chase Young is this to [[spoiler:Master Monk Guan]] from before Chase was [[DealWithTheDevil turned Heylin by Hannibal Bean.]] [[spoiler:Technically, he is this to Grand Master Dashi as well, except that Dashi is assumedly dead in the present.]]
* In [[WesternAnimation/TheTransformers the original Transformers cartoon]], Starscream used to be Skyfire's best friend before the war.
** Similar to Cy-Kill and Leader-1 below Optimus and Megatron used to be close as brothers in ''WesternAnimation/TransformersPrime''.
* Cy-Kill used to be Leader-1's closest comrade in ''WesternAnimation/ChallengeOfTheGoBots.'' He defected out of jealousy over Leader-1's successes.
* In ''WesternAnimation/{{MASK}}'', Matt Trakker and Miles Mayhem were friends who formed MASK together, before Mayhem stole some of the masks and used them to set up VENOM.
* Wheeljack in ''Anime/TransformersArmada'' was friends with Hot Shot before Hot Shot betrays him...or so Wheeljack thinks. Turns out Hot Shot tried to go back and save him, but failed.
* In ''Toys/{{Bionicle}}'''s 2004 line, Lhikan and Nidhiki use to be close friends as Toa, but Nidhiki betrayed his fellow Toa to the Dark Hunters. When his plan failed, Nidhiki was transformed into an insectoid monster.
* In the ''WesternAnimation/CaptainNTheGameMaster'' episode "The Most Dangerous Game Master" Dr. Wily builds an android rival based on Kevin's memories of a school bully. Later we find out Kevin and the bully used to be friends, and since the bully was created from Kevin's memories he still retains his good traits and Kevin is able to befriend him again.
* General Modula, the BigBad of ''WesternAnimation/SymBionicTitan'', was this to the King of Galaluna prior to the series, also as seen in a flashback in "Shadows of Youth."
* [[CainAndAbel Nightmare Moon to Princess Celestia]] in ''WesternAnimation/MyLittlePonyFriendshipIsMagic''. Prior to her FaceHeelTurn, she was Princess Luna, a co-ruler of Equestria alongside her sister. [[spoiler:They eventually patch things up once Luna is purged of her SuperpoweredEvilSide and its influence.]]
* In ''WesternAnimation/{{SheZow}}'', Tara was the sidekick to Guy's aunt Agnes, the previous [=SheZow=], but eventually faded into obscurity. When she first appears she wants to bury the hatchet, but Guy not knowing who she is causes her to snap and challenge him to a duel instead, namely "GLAMAGEDDON-GEDDON-GEDDON!"
* In ''WesternAnimation/ElTigreTheAdventuresOfMannyRivera'', White Pantera's ex-sidekick, the Titanium Titan, turns evil after White Pantera's son Manny was born and resents him for having his partner's attention. He becomes obsessed with getting rid of El Tigre so he can have White Pantera to himself again.
* Penny to Bessie from ''WesternAnimation/TheMightyB''. She also conbined this with TheEeyore and WoobieDestroyerOfWorlds tropes.
* Nester to Scaredy in ''WesternAnimation/ScaredySquirrel''.
* Demona, one of the main villains in ''WesternAnimation/{{Gargoyles}}'', was a member of the Gargoyles' clan and Goliath's lover before she became evil.
* Not close friends, but WesternAnimation/DarkwingDuck and Megavolt went together to the same high school, and they were both bullied by the same crowd.
* According to Gobbler, Stoic and Alvin use to be friends in ''WesternAnimation/DragonsRidersOfBerk'', having a LoveHateRelationship similar to that of Hiccup and Snotlout in the present.
* ''WesternAnimation/ShimmerAndShine'': In "Samira and Zeta", it's revealed that Samira and Zeta used to be friends until Zeta became resentful of Samira's progress as a genie-in-training.