Rival Turned Evil

"The Heartless obey me now, Sora. Now I have nothing to fear."

"I'll hug my rival, but to smother him."

— Nero from Jean Racine's Britannicus, act iv, scene iii

Two characters are (or were) clearly friends; the innocent lead's friend probably had a dark past or was shunned by others, but nonetheless they managed to become friends.

However, at some point, their playful rivalry starts to escalate (a one-sided affair, usually) or they simply drift apart because of the plot. Often times the powder keg is a single event that breaks the increasingly tenuous friendship, at which point one friend becomes the villain. This can be part of a newly revealed dark past, or dealing with a major problem in a way his friend or other people can't tolerate. Sometimes it's just a very minor misunderstanding no one seems interested in clarifying.

This is a common fate for The Rival and certain types of Lancers, especially if they were the lead character's friend and Missed the Call, or if they grew up with a third, female friend.

If the main character is a Messianic Archetype or even just has a strong connection with his True Companions, expect him to make it his mission to turn his friend back to the side of good even while everyone else is trying to kill him. Whether he succeeds or fails in this mission becomes a source of much drama for the character. Meanwhile, the rival turned villain's job is to dredge up all his pent-up feelings of jealousy to try to justify his actions often becoming his own worst enemy in the process.

If the rival is a sibling, it's Cain and Abel. Contrast Rivals Team Up and Driven by Envy.

Sister trope of The Rival. May or may not be The Resenter. Compare Arch-Enemy. See also Evil Former Friend and Rival Final Boss.

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Examples:

Anime & Manga

• Afro and Jinno in Afro Samurai. Interestingly, it's the protagonist, Afro, who "turned evil" — everything Jinno does is to protect those at Swordmaster's dojo, while Afro is motivated purely by revenge.
• In Battle Spirits Shonen Toppa Bashin, happens with J. The truth was that J had his own objectives and had no desire to cooperate with the plans of Numbers Elite. In fact, he actively tried to sabotage them even while as a member. But because of this, he still ends up betraying Bashin.
• Cardfight!! Vanguard loves this trope. In Kai's backstory, he becomes friends with Ren Suzugamori after transferring to the same school which Ren attends. Ren soon obtains Psyqualia and begins losing his sanity before the start of the series, while Kai, having no idea how to save his friend, decides to leave Ren behind and move back to the town where Aichi lives. Kai walking out on Ren actually made things worse. Then, we move on to the beginning of the story proper, where Kai has taken up a cold and distant approach in an attempt to keep history from repeating. He does end up joining a team with Aichi Sendou, only for Aichi to start developing Psyqualia and losing his sanity as well. Thankfully, they both regain their sanity by the end of the first season.
  • However, in the third season, Kai is the one to turn evil this time, as he winds up being reversed after his fight with a reversed Takuto and going so far as to take up the very clan that embodies Void.
• Code Geass:
  • Lelouch is an inverted form of this trope. Lelouch's philosophical disagreement with Suzaku over whether to destroy Britannia or fix it from within leads to the two childhood friends at gunpoint in the Season 1 finale. In R2, Suzaku and Lelouch come to the conclusion that there's a better option than destroying Britannia or fixing it from within doing both.
  • Temporarily reversed in R2 when Suzaku is seen to be playing for Charles but instead of them turning on each other, Suzaku eventually joins forces with Lelouch to put an end to the wars altogether.
• Yui and Haruna in Corrector Yui. Though Haruna gets better more or less quickly.
• Spike and Vicious in Cowboy Bebop, although this is probably an inversion — Vicious didn't turn evil (it's pretty clear he was always a sociopath) so much as Spike turned good (or at least turned neutral), but it is implied that Vicious didn't use to be this much of a sociopath, and Spike's betrayal pushed him over the edge.
• In Demon Slayer: Kimetsu no Yaiba, Kaigaku was once Zenitsu's rival as fellow students before being corrupted into a demon by Kokushibo, but it's clear he was already not a nice person before his demonization.
• Digimon Adventure does this very briefly with Yamato/Matt, though it's also slightly downplayed as he wasn't exactly evil. After Cherrymon makes him realize that his rivalry with Taichi/Tai is what's clouding his heart, he effectively forces a duel between WarGreymon and an unwaveringly loyal MetalGarurumon, which then quickly devolves into fisticuffs between the two tamers. After Homeostasis possesses Hikari/Kari and gives a lengthy Info Dump, a remorseful Matt exiles himself from the group for the next few episodes to atone for his mistake.
• In the Ice and Snow arc of D.N.Angel, Kyle, Elliot's best friend does this because of the Two Guys and a Girl scenario. He's eventually doomed a la Rime Of The Ancient Mariner to tell the story so others don't make his mistake after he causes BOTH of their deaths. Sort of. It's complicated.
• In the Buu Saga of Dragon Ball Z, Vegeta had enough of being Always Second Best to Goku, so he willingly let Babidi brainwash him so he can get the power he needed to fight Goku once and for all. Goku only had one day on earth due to being dead and Vegeta would never have another chance at besting him and threatened to kill anyone until Goku gave in. This unfortunately set off a chain of events that led to Buu's resurrection due to the intensity of their duel.
• In the anime version of Dragonaut: The Resonance, Kazuki and Jin started out as friends. Jin was forced to drop out of the program they were both working in during an accident which ultimately resulted in Kazuki's Dragon rejecting him and accepting Jin. When Kazuki finally gets a Dragon and ends up fighting Jin, he gets badly scarred, causing him to hate Jin even more.
• Kenshiro and Shin from Fist of the North Star were friends from different martial art schools who were in love with the same woman until Jagi, Kenshiro's jealous brother, swayed Shin into betraying Kenshiro and taking Yuria for himself.
• Yui in Fushigi Yuugi decides to turn against her childhood best friend, Miaka. She gets better after realizing her mistakes and Nakago's betrayal.
• Megumi from Gate Keepers who turned traitor because she envied Ruriko's seeming superiority.
• Played with in Glass Mask. When both actresses who are competing for the iconic role of Crimson Goddess arrive on the island where the film has always taken place, Ayumi notices a weak wooden bridge ready to give out and is smart enough not to cross it. Later on, Maya, her rival for the role, tries to cross the bridge. Ayumi sees this and thinks that letting Maya die would finally eliminate the threat to her future superstardom. But she changes her mind at the last minute, right when the bridge does give out, and saves Maya's life. She confesses to Maya about it out of guilt, which leads to the two girls fighting and making it clear where they stand with each other out of respect.
• Kenichi: The Mightiest Disciple works this in, but it's among the many things Kenichi has *forgotten* since his childhood. Big Bad Odin is really a childhood friend who made a promise with Kenichi that they would both get stronger... before insisting on fighting over a pin Kenichi received. Odin reveals that it was the loss in that childhood fight, coupled with the humiliation of being offered the pin afterward anyway, that set him on the Path of Asura.
• In Macross Frontier, Ranka temporariliy turns evil, at least from the human perspective, due to Mind Control. Then she breaks out of it with the help of Sheryl and in return saves her life
• In Mobile Suit Gundam Wing, Milliardo and Treize, but it is more of Civil Warcraft
  • And in Mobile Suit Gundam SEED, Kira and Athrun towards each other.
  • Similarly, Asemu and Zeheart from the second generation of Mobile Suit Gundam AGE, only with Zeheart being a spy in the first place, and him being friendly part is a bit of Becoming the Mask.
• Nina and Arika's humorous Odd Couple relationship in My-Otome disintegrated due to a number of... misunderstandings, to put it mildly. They started out as rivals in academics as a result of Garderobe only allowing a limited number of students to advance, but over time, the rivalry is over the love of Nina's adoptive father Sergay. When it turns out that Sergay is anonymously supporting Arika, Nina becomes Nagi's Otome and tries to kill Arika.
• Enchu for Muhyo in Muhyo and Roji. Initially, his grades were far superior to Muhyo's because he put in the effort while Muhyo did not, but as Muhyo's talent awoke, he began surpassing Enchu. This was a particularly sore spot for Enchu, as he hoped to become an Executor to support his sick mother. Losing the position to Muhyo shortly after losing his mother broke Enchu and resulted in his Face–Heel Turn. It turns out that Teeki invoked this trope to find a powerful body to take as his own, and killed Enchu's mother to turn him evil.
• My Hero Academia: The League of Villains attempts to Invoke this when they kidnap Deku's rival Bakugo, who not only is envious of Deku's progress, but is notoriously violent, arrogant, and bad-tempered, and by all accounts is more suited to being a Villain than a Hero. Defied, however; for all his faults, Bakugo does want to be a hero, and tells the League to go to Hell.
• Sasuke and Naruto in Naruto is the definition of this. Interestingly enough, though, the rivalry started out one-sided and became mutual as Naruto got stronger.
  • Apparently, it goes across for many generations in the world of shinobi:
    • Hashirama Senju and Madara Uchiha.
    • Hiruzen Sarutobi and Danzo Shimura.
    • Jiraiya and Orochimaru.
    • Even Mifune and Hanzo.
    • Tobi, aka Obito Uchiha and Kakashi Hatake.
• In Tokyo Ghoul, the office rivalry between Akira Mado and Seidou Takizawa escalates into this as a result of his transformation into a Half-Human Hybrid and descent into madness. He initially attempts to reconcile with her by playing hero, but receives a harsh rejection from his former allies and rival. It isn't until Mutsuki tries to kill him that Akira realizes her mistake and protects him, helping bring him back to his senses.
• Yu-Gi-Oh!:
  • Yu-Gi-Oh! weirdly inverts this with Seto Kaiba. In the manga, he started out as a homicidal Creepy Child-like villain who tried to outright murder Yugi and his friends, even trapping them in a deadly maze all for the sake of revenge against Yugi for beating him at his own game. Being soundly defeated with a Penalty Game to the point of going near comatose, along with a shown Freudian Excuse, made him develop into the straight Stock Shōnen Rival obsessed with defeating Yugi in a duel that he's most widely known as. The anime dropped this early villainous phase of his entirely (due to Adaptation Distillation condensing all of the earlier arcs into either flashbacks or the very first episode to focus on the Duelist Kingdom arc), making him merely The Rival from the start. So for him, this trope is more "Evil Turned Rival".
  • Kaiser Ryo in Yu-Gi-Oh! GX occupied an odd spot in between The Ace and The Rival in Season 1, before having a Freak Out in Season 2. Oddly enough, despite at least two attempts to break him out of it, neither succeeded. In fact, he gets better all on his own. Even before that, he's still something of a jerkass protagonist in the second half of Season 3.
  • And speaking of Yu-Gi-Oh, Yu-Gi-Oh! 5Ds's Kiryu Kyosuke was the lead's best friend as the leader of Team Satisfaction, but he got too... excited by the whole conquering-Satellite thing. When he tried to duel all of Security (the police force) and ended up killing one of them, leading to a situation where he believed that Yusei had turned him in to the police, Yusei's and Kiryu's friendship got shot to hell. Kiryu died, which ironically meant that he got better and everything else got worse at the same time. And by everything else, that means he got so Ax-Crazy you could make a case of him reaching critical, Dilandau Albatou levels.
  • Also from 5D's, Jack Atlas. Prior to the series setting, he was also a member of Team Satisfaction and a friendly rival to Yusei. He grew more and more distant from his friends following the break-up of the team, and eventually accepted an offer to become King in return for betraying Yusei by stealing his D-Wheel and Stardust Dragon, which he accomplished by endangering Rally's life. He's by far a less extreme example than Kiryu, though, as this was the last truly evil action he took, and once Yusei settled their score he quickly became a protagonist and sought redemption in the second season.

Comic Books

• Catwoman: Cassandra Cartland grew up in the same orphanage as Selina Kyle where Selina rebuffed Cassandra's attempts at friendship. Cassandra grew bitter and resentful and, after learning that Selina had become Catwoman, created her own villainous identity of She-cat and attempted to frame Selina for crimes she committed.
• Doctor Strange had Baron Mordo, until he reformed while dying of cancer. And then he was brought back as a villain because the writers either forgot about his reformation or were just too lazy to create a new evil sorcerer.
• Subverted in ElfQuest. Rayek starts out as Cutter's rival of sorts. Several times in the story, he appears to be about to turn evil, but despite his screwups, he never does, at least, not permanently. Rival Turned Heel–Face Revolving Door?
• Doctor Doom and Reed Richards are probably one of the most straightforward examples of this trope. The catalyst for Doom turning evil was an incident where Reed pointed out a flaw in one of Doom's projects (An artificial Hell Gate to Mephisto's realm) when they were both classmates in grad school rivaling for the spot of top student, and Doom, thinking Reed was just jealous, ignored him, only for the project to blow up in his face, disfiguring him and getting him expelled. Doom was so infuriated by the idea that that infernal Richards had bested him that he rejected that version of reality, blamed Reed for the accident, and dedicated himself to destroying Reed's life in "revenge".^note  Apparently, accidentally bruising the ego of the great Victor von Doom makes you deserving of constant stalking, murder attempts, targeting of your wife and friends, forced duels, repeated physical and psychological torture, mind rape, attempted genocide of your country, kidnapping your kids, screwing with your head and ill-handled guilt complex until you almost lose your mind/fly into a homicidal rage, and turning your life into one long, exhausting, never-ending hell.
  
  The "rivalry" part of their relationship (in addition to the blinding, obsessive vendetta) is still in full force, as the reasons for all of Doom's evil plans to Take Over the World, gain cosmic power, topple governments, decimate the superhero community, and rain death and destruction upon all oppose him can eventually be traced back to his desire to get one over on his old college pal. (He'll even delay killing Reed to make him admit Doom is better than he is.)
• Iron Man:
  • Tony Stark gets one for a short time in the form of Tiberius Stone, who's implied to have been a sociopath from the beginning, just very good at hiding it. "Short time" because by the end of the arc, Stone has been left comatose, and tends to be forgotten by later writers.
  • Obidiah Stane also served this purpose.
• Legion of Super-Heroes: Some versions of Lightning Lad's relationship with his brother Mekt (Lightning Lord) go this way.
• This was inverted in the 70's Marvel Universe comic Shang-Chi, Master of Kung Fu. As an acolyte of the despotic ambitions of his father, Fu Manchu, Shang-Chi was always just a little better than his childhood friend, Midnight. But in this case, it was Shang-Chi who turned, rejecting his father's evil and leaving the organization. Naturally, his old friend got sent after him. Said friend added a righteous sense of betrayal to his previous resentment.
• In Shaman's Tears, Thom Broadarrow was a childhood rival to Joshua Brand. He was always jealous of Joshua, especially when Joshua got the girl they both wanted, then abandoned her to leave the reservation; something Thom never managed. When Joshua, returned to the reservation and was granted the power of Wakan Tanka, Thom thought it should have rightfully been his. His jealousy ultimately led to the accident that transformed him into a monster.
• Sonic the Hedgehog (Archie Comics): Sonic's old rival Geoffrey St. John was revealed to be working for Ixis Naugus, and is implied to have been working for him for some time. As it turned out, Geoffrey has always worked for Naugus — as in, before either was even introduced into the comic — so this isn't so much "Rival Turned Evil" as it is "Rival Who's Always Been Evil But Playing Good".
• Spider-Man: Eddie Brock was a reporter that developed a grudge against Spider-Man when the latter apprehended Sin-Eater. Brock had been interviewing a compulsive confessor and lost his job in disgrace. In addition to his job loss and inability to find a new one in journalism barring tabloids, he was also diagnosed with terminal cancer, so when he encountered the symbiote (which had tracked Brock by his negative emotions and the cancer upon which it feeds) in the church where Spider-Man had abandoned it, he was more than willing to use the symbiote to get the revenge he craved... armed with the knowledge of Spider-Man's secret identity and calling himself Venom in reference to the types of articles he was paid to write. He ultimately reformed and gave up the symbiote knowing that without it he would eventually die of the cancer ravaging his body. Except... the trace of the symbiote in his blood fused with white blood cells and created the menacing Anti-Venom, who, while not as evil, fights villains like the current Venom Mac Garnagan (AKA: The Scorpion), still holds a grudge with ole Spidey. Oh well.
• Superman:
  • Conduit was once a childhood rival and friend of Clark Kent but tried to kill him years later.
  • So was Lex Luthor, at least in the Silver Age continuity. Though he had a friendly rivalry going with Superboy not Clark.
• Tragg and the Sky Gods: Gorth was a tribesman who always resented the handsome and talented Tragg. This simmering hatred allowed Zorek to transform into the Beast Man Sabre-Fang: half-man/half-sabretooth tiger. Sabre-Tooth was turned loose with one overwhelming compulsion: to hunt and kill Tragg and Lorn.
• The Warlord: Danny Maddox grew up in the same town as Morgan, and always felt in Morgan's shadow, and blamed Morgan for everything that went wrong in his life. (This rivalry was almost entirely one way, with Morgan barely knowing that Maddox existed). His attempts to beat Morgan drove him deeper and deeper into evil acts. Maddox was the pilot responsible for shooting down Morgan's plane and causing him to crash in the Lost World of Skataris and, years later, Maddox would descend into Skataris himself in am attempt to prove his superiority to Morgan once and for all.
• Wolverine: In Origin, Dog starts out as James Howlett's friend and secret half-brother, but eventually they drift apart, and Dog even kills James' puppy. James eventually runs away from home after an incident causes the death of his parents and Dog's father, and Dog tells the locals it was James' fault. Years later, Dog is told to track James down so that James' grandfather can make amends, but instead Dog tries to kill James for taking his name (Logan). This one also works for Two Guys and a Girl, with James, Dog, and Rose. Dog is later tracked down by Sabretooth, Logan's other rival turned evil when he ends up in the present and is hired as a teacher at the Hellfire Academy.

Fan Works

• Nami and Elly in Pirate Meets Gebler when the latter used the Drive to not only fight Fei, but also the former. They got better after the former got the latter to snap out of this by threatening to drop herself off the canyon.

Films — Live-Action

• In The Count of Monte Cristo, Dantes and Mondego are good friends with a friendly rivalry before Mondego betrays Dantes out of jealousy.
• While he and Ip Man never became friends, Jin descended from martial artist rivalry to becoming a bandit and later selling Ip Man's last known whereabouts to the Japanese. He does a Heel–Face Turn back by the second film.
• Like his comic counterpart, Iron Man had his fair share of evil rivals. The first was Obidiah Stane who, in the Marvel Cinematic Universe was an in-company rival to Stark Enterprises as opposed to the head of his own company. He eventually turned evil and tried to kill Stark. In the second film, Justin Hammer was a business rival who ended up releasing an international criminal who had previously killed many people and tried to kill Stark, in order to defeat Stark Enterprises.
• Ben and Ian in the first National Treasure movie.
• The escalation of this effect drives the plot of The Prestige. Robert Angier and Alfred Borden are both amateur magicians working fairly amicably as audience plants for another magician. However, when Angier's wife is killed and Borden appears to be responsible (it's possible that he's entirely innocent) Angier devotes himself to destroying Borden by any means including sabotaging and stealing his tricks as well as killing himself dozens of times over just so he can eventually frame Borden for murder and take his daughter. Borden remains far from innocent though and retaliates by constantly ruining Angier's chance at fame and stealing his mistress.
• Overlaps with Love Makes You Evil in The Sorcerer's Apprentice. Maxim Horvath was a friend of Balthazar Blake and was in love with Veronica Gorloisen, with all three being Merlin's apprentices. Veronica chose Balthazar, resulting in Horvath deciding that he no longer cared about anything and would willingly help Morgana destroy the world and is not shy about trying to kill Balthazar. Centuries later, Balthazar is surprised that Horvath still feels bitter about Veronica's choice.
• Spider-Man Trilogy: Eddie Brock is portrayed this way in Spider-Man 3, as fighting for Peter's position at Jameson's office. The Rival/Evil Turn comes after he tries to cheat his way ahead and Peter exposes him; Peter, wearing the Venom suit, goes to a local chapel seeking repentance, while Eddie goes to the same seeking revenge; the church bells ring, disturbing Venom sufficiently that Peter is able to fight him off, and Venom drops down a few stories to take over Eddie, who is a much more willing host...

Literature

• Faquarl of The Bartimaeus Trilogy was already evil, but he's The Rival of the titular character and a White Hair, Black Heart, so he fits.
• Pasha in Doctor Zhivago, though he was Lara's friend (and thus more of a romantic rival for Yuri).
• Happens with Brutus in Con Iggulden's Emperor series. He starts out as Caesar's loyal blood brother, but as time goes by he grows increasingly jealous of his friend's success as a general and a politician. Eventually he leaves Caesar to fight for Pompey in the civil war and tells Caesar later that he did it because he wanted to be someone without having to stand in the shadow of the great Caesar.
• Fengshen Yanyi: Shen Gongbao, introduced during Jiang Ziya's first return trip on Kunlun, was Ziya's co-disciple and studied alongside him, making more progress on the path of magic. However, he thinks that Jiang Ziya's task of helping the Zhou Dynasty against the corrupt Shang one is a fool's errand and that King Zhou should be the legitimate ruler of the land, despite having being forsaken by Heaven for his impiety and cruelty. He tries to bully his younger friend into giving him the Fengshenbang (the list of the 365 illustrious characters who'll become gods after the war) and joining the Shang, using his greater mastery of sorcery to make him comply. Even when he's thwarted but spared thanks to Ziya, Shen Gongbao swears revenge and spends the rest of the novel spreading lies and deceit to make otherwise neutral or uninterested Immortals attack the city of Xiqi and the forces of Zhou. After finally killing Jiang Ziya (who gets better, as he was destinated to die seven times) he's finally captured but spared on the condition that he stops pestering the forces of Xiqi. He breaks his oath siding with the Jie Taoists during the great war at the Ten Thousands Immortals Formation and pays with his life.
• Harry Potter:
  • James Potter and Severus Snape never got along at school, made worse by the fact that Lily, Snape's childhood friend who he was thoroughly in love with, ended up marrying James, while Snape turned evil. Snape turned back to the side of good because Lily was in danger, and stayed on the good side because his previous evil actions caused her death.
  • Played With: Harry's own rival, Draco Malfoy, was pretty petty in the early books, but when Voldemort returns to power, he joins him. He winds up causing a lot of damage in the sixth book, but he also can't bring himself to actually murder Dumbledore, and he's clearly terrified of all of the actual psychopaths whom he's forced to work with. He never technically switches back to the good side until Voldemort's defeat, but he's so scared and pathetic that Harry briefly pities him.
• The Inheritance Cycle: Murtagh pulls a Face–Heel Turn while everyone else thought he was dead. Supposedly this is because the Big Bad knows his true name, but he also displays some jealousy of his brother Eragon. Unlike other examples, he is surprisingly reasonable about it, including sparing Eragon's life.
• The Lord of the Rings: One of the reasons that Saruman got corrupted is because he was jealous of Gandalf having received the Ring of Fire from Círdan upon their arrival in Middle-Earth. This is made clear in Unfinished Tales of Númenor and Middle-earth.
• At the end of Graham McNeill's Ultramarines novel Dead Sky Black Sun, Honsou corners the Space Marine Vaanes, who had helped Uriel against Honsou before deciding that it cost too much. Honsou offers to let him work for the Chaos forces and promises Revenge, and Vaanes accepts. Sequel Hook, anyone?
• Breezepelt from Warrior Cats was originally the rival to Lionblaze and Jayfeather, but he was friendly enough to team up with them on occasion. However, in Omen Of The Stars he is recruited by the Dark Forest and turns homicidal.
• It seems as if half the Forsaken in The Wheel of Time had been very talented and effective good guy generals and Aes Sedai who could not stand that their rival Lews Therin Telamon (whom they were at least fairly friendly/neutral colleagues with at one stage), The Dragon, was better than them, thus turning to the Dark One (Not the case for other Forsaken like the sadistic, and unparalleled healer, Semirhage, or The Philosopher Ishmael).
  • Played most straight with the Forsaken Demandred. His entire life can essentially be described as "almost as good as Lews Therin". He was born a day later. He was ever so slightly weaker in the Power, and ever so slightly less proficient at its use. He was slightly shorter. He was slightly worse looking. Ilenya chose Lews Therin over him. He was passed up for becoming the Amyrlin Seat in favour of Lews Therin. Lews Therin's deeds in the War of Power were slightly more impressive. So on and so forth. Characters from the time who think back say that in any other time, in any other place, he could have been the greatest hero of the age, but he had the misfortune to be born into Lews Therin's time. He fell to the Dark primarily out of jealousy for Lews Therin, and to this day is described as the Forsaken with the most hate (particularly for Lews Therin, but in general as well). Not the most anger, not the biggest ego, not the most sadistic; he just hates.

Live-Action TV

• 24's Jack Bauer seems to have an endless string of these, particularly Christopher Henderson.
• Bones: Booth and Broadsky served together as snipers in the military; while Booth later returned to civilian life, Broadsky became an assassin-for-hire, exacting revenge against the criminal element on behalf of his 'clients'.
• Buffy the Vampire Slayer: Buffy and Faith interacted this way, sliding in and out of rivalry as the story progressed.
• The Master and The Rani from Doctor Who are two examples as well (spin-off media has suggested that this applies to the Monk and the War Chief as well, as all five Time Lords were basically part of the same study group back at the Academy).
• Family Matters had a one-time antagonist by the name of Dexter Thornhill in Season 5's "Presumed Urkel". He was Steve Urkel's academic rival, from always taking second place in the science fair while Steve took first every year to always calling Steve "Yuckel". Thornhill became so jealous of Steve over the years, he tried to get him expelled from Vanderbilt High School by framing him for blowing up the school science lab by tampering with his latest science project, a graffiti remover, by filling his beaker with explosive chemicals and turning up the Bunsen burner to the maximum point. Laura, who was still annoyed of Steve's constant calls for love at the time, agreed to defend him in Vanderbilt's student court, where she eventually outs Thornhill as the true culprit, upon which he himself is expelled and likely sent to juvie.
• Justified: U.S. Marshal Raylan Givens and Harlan County marijuana dealer Dickie Bennett were high school baseball rivals, whose enmity turned deeply ugly when Dickie attacked Raylan during a game, starting a fight that left Dickie with a permanent limp and an undying grudge, and nearly reignited a long-buried feud between the Bennett clan and the Givens' family. Decades later Raylan and Dickie find themselves on a collision course again, and for Dickie at least, It's Personal.
• Kamen Rider:
  • In Kamen Rider 555, Takumi and Kiba switch back and forth between friends and enemies, not once but several times. Eventually, Kiba does a Face–Heel Turn and becomes an all-out villain, but in the last episode he returns to the Light Side and does a Redemption Equals Death.
  • Kamen Rider Gaim: At different points in the story, Kaito Kumon is Kouta's worthy rival and key ally. By the end, he's become an Evil Overlord bent on forcefully righting the world's wrongs and Kouta's final opponent.
  • Kamen Rider Ex-Aid has an interesting example. A 14 year old Kuroto came to view Emu as a rival after seeing he had game ideas that were as good as his and infected him with the Bugster virus out of spite, but Emu wasn't even aware of this until the two were adults and Kuroto had long since become a godhood-seeking megalomaniac.
  • Kamen Rider Geats has two examples at different points in the story:
    • Michinaga Azuma is a DGP participant and Ace's rival who vows to one-up Ace in the DGP. Later he pulls a Face–Heel Turn by joining the Jyamato faction.
    • Though Keiwa's more of a Friendly Rival to Ace than Michinaga, he becomes colder towards Ace when he learns that Mitsume, the Goddess of Creation that fuels the DGP's wishes and consumed his parents for wish fuel, is Ace's mother. Losing his sister Sara on top of learning that makes Keiwa just as bitter toward Ace as Michinaga was, until he's able to put his resentment behind him and become Ace's ally again for the last episodes of the show.
• Rizzoli & Isles: Alice Sands, the Big Bad in Season 6 (and part of Season 7) attended the police academy with Jane. Alice was second in her class behind Jane, after having been the best at everything prior to then. This created her dangerous fixation on Jane (although it should be noted that Jane never considered Alice a 'rival' in turn as it's suggested she never really interacted with Alice back in the day). She dropped out of the academy and became a drug dealer. Years later she would return, determined to destroy Jane's life before killing her.
• The early seasons of Smallville dealt with Clark and Lex's relationship this way.
• Star Trek: Worf and Gowron had a friendship in Star Trek: The Next Generation that was at times uneasy due to Worf's values and integrity. When Gowron had the Klingon Empire invade the Cardassians in Star Trek: Deep Space Nine Gowron broke off the friendship when Worf refused to support the invasion and remain loyal to the Federation. The pair put their differences aside during the Dominion War, but when Gowron began trying to get General Martok killed Worf had enough of Gowron's corruption and challenged him to a fight to the death.
• The Vampire Diaries' Damon got his Start of Darkness this way. The antagonistic relationship between him and Stefan began with their rivalry for the affections of Katherine.

Music

• "Enemy" by Fozzy apparently is about two people who were once friends and then had a breakup of some kind and the lyrics talk about they will always be on opposite sides.

Professional Wrestling

• Low Ki and Xavier had feuded and made up for years beforehand, but Xavier had officially crossed over to evil when he joined The Prophecy to abolish the honor code and remake ROH in the image of Christopher Daniels. Also part of the Prophecy was Samoa Joe, a token good teammate Only in It for the Money who refused to violate the honor code, which made Low Ki the rival turned evil when he went on a hiatus from the company and returned as a member of the Rottweilers, spitting on Joe's ROH Championship belt after he defeated Xavier.

Theatre

• In Hamlet, It's unclear how close Hamlet and Laertes have been, but King Claudius's thinly-veiled preference for Laertes over his nephew (and purported adopted son) clearly casts the two as rivals. Justifiedly, after Hamlet accidentally kills Laertes's father, the two become enemies, and eventually take each other down with the same poisoned foil.

Video Games

• Jake from Ape Escape is turned into Spike's enemy by Spectre's brainwashing.
• Tsubaki Yayoi towards Noel Vermilion in BlazBlue. Thanks to Terumi's influence, Tsubaki grew to resent Noel for having the position as the secretary of her love interest. To twist it even further, she finds out that in another timeline, she would have had said position if Noel never existed. Thankfully, they resolve their issues by the time of the third game and reconcile.
• One of the plotlines of Breath of Fire: Dragon Quarter mostly follows this trope. Ryu and Bosch start the game, while not necessarily as mutual friends, at least as co-workers. When Bosch starts observing (and once ends up on the wrong end of) Ryu's suddenly-manifested dragon powers, he jealously begins resorting to increasingly twisted means to match that power, including getting a freaky cybernetic body and, eventually, gaining similar powers from an evil dragon, after it sensed his selfish motives.
• Castlevania:
  • Maxim in Castlevania: Harmony of Dissonance, but only because a manifestation of Dracula took over his body.
  • Before that, Hugh Baldwin in Castlevania: Circle of the Moon. He's the son of his and Nathan's master, and is jealous enough of Nathan getting the Hunter whip that he turns evil and is fought as the second-to-last boss.
  • In Castlevania: Legacy of Darkness, Ortega resented Cornell for his greater mastery over the man-beast power. This drove him to serve Dracula (slaughtering their home village and kidnapping Cornell's adopted sister Ada in the process) in exchange for greater power. This culminates in Ortega being the penultimate boss in Cornell's storyline, where he demonstrates the power Dracula gave him by turning into a chimera. It's only after Cornell defeats him again that he comes to his senses and tells Cornell what he needs to do to save Ada. It's Redemption Equals Death though since he can't control the power Dracula gave him anymore and he hurls himself off the roof, much to Cornell's dismay.
• In the backstory for City of Heroes / City of Villains, the men who would become archnemeses Statesman and Lord Recluse were once very good friends. When they drank from the Well of the Furies, one became an Incarnate of Zeus, got lightning powers, and named himself Statesman, while the other became an Incarnate of Tartarus, grew spider arms, and named himself Lord Recluse. One of them became an evil overlord.
• Caim and Inuart in Drakengard. Inuart is helped along his Face–Heel Turn by More than Mind Control.
• EarthBound (1994): Ness and Pokey, though it's unclear if they were ever friends; Ness is at least on better terms with his brother. Pokey starts out as a bit of an obnoxious and cowardly bully from the unhappy house next door who tags along with Ness during the beginning, with everything going downhill as he leaves town and starts to help out increasingly dangerous antagonists met across the journey, to the point of becoming the most active obstacle in Ness's goal to save the world. This descent definitely wasn't helped by being consistently close to the Mani Mani Statue, or that Giygas is known to corrupt the minds of earthlings during the story. Oddly for the trope, Pokey doesn't seem to know what he wants to be as far as Ness goes, which makes a lot of sense considering he's a lonely kid from a turbulent household, and it's increasingly hinted that despite his actions and outward demeanor, he really does want to be friends with Ness. In Mother 3, you can find Ness' yo-yo in now-Big Bad Porky's playroom in the thunder tower, and it's named "Friend's Yoyo".
• Final Fantasy:
  • Cecil and Kain in Final Fantasy IV. Kain was being (at least partially) mind-controlled, and he repents eventually, but his jealousy over Cecil (mostly regarding Rosa) makes him that much easier to control.
  • Seifer Almasy in Final Fantasy VIII, who starts off as a Jerkass rival to protagonist Squall Leonhart before going all in and siding with the Sorceress Edea.
• Fire Emblem:
  • In Fire Emblem: Mystery of the Emblem there's Arlen, who betrays his nation after his mentor Wendell gives Merric the Excalibur magic tome. He gets better after Wendell points out he is walking down the same path Gharnef once did.
  • In Fire Emblem Fates: Conquest, Takumi starts off as a heroic individual. However, his obsession with killing you for betraying Hoshido eventually grows out of control, and with the help of a little Demonic Possession, he turns into an Ax-Crazy madman and the Final Boss of the route.
• Ryudo and Melfice in Grandia II were in fact brothers, but like everybody from their soon-to-be-cursed village very competitive. Melfice turns out to be possessed by the Horns of Valmar, forcing the brothers to fight. Additionally, Ryudo meets up with his childhood friend and rival who has to admit he's become soft and Ryudo is currently a better swordsman than him, at least until he starts training again.
• Yashu from Half-Minute Hero: The Second Coming. His rivalry with the main hero Yusha starts out friendly, but Lamde (an antagonist from the previous game) exploits his fanatical devotion to Queen Maria and, through a series of machinations and tragic misunderstandings, causes Yashu to go berserk and swear revenge on Yusha and all of his descendants.
• Rosh Penin in Jedi Knight: Jedi Academy was apprenticed to Jedi Master Kyle Katarn alongside Jaden Korr, and saw Jaden as his rival. This bitterness and his feelings of inferiority led to him being manipulated by the Disciples of Ragnos and led to the Dark Side before being redeemed by Jaden.
• Sora and Riku in Kingdom Hearts (pictured above). Riku turns to the dark side by More than Mind Control, and is eventually possessed by the Big Bad. After he's freed from this possession at the end of the game, he spends Chain of Memories and Kingdom Hearts II dealing with the consequences in a quest for atonement. It's especially interesting that Riku fits all three of the marker tropes at the top of the page: he was supposed to have the Keyblade, has very nearly white hair, and grew up with Sora and Kairi.
• Songi starts as Gala's rival in Legend of Legaia. He quickly turns more and more depraved and villainous in his journey for greater power.
• Streibough in the Medieval chapter of Live A Live; jealous of his childhood friend Oersted's fame and success, he ultimately orchestrates a plan intended to thoroughly disgrace and break him. Whether he intended it or not, he ultimately ends up causing Oersted to undergo a major Face–Heel Turn, declaring that Humans Are Bastards and becoming the game's Big Bad. So, in the end, both rivals turn evil.
• Steiner is blatantly set up for this in Luminous Arc 2, although it's worth noting that from his viewpoint, the hero has turned evil (having collaborated with several criminals, one of whom was an accomplice to a mass murderer.) The two go through the standard "redeem each other or kill each other" schtick before Steiner sacrifices himself to kill a greater villain.
• There have been three cases of this in the Sly Cooper games.
  • Neyla of Sly 2: Band of Thieves is a rival to both Sly and Carmelita, but she's respectively on good and neutral terms, and helps Sly out a few times. She betrays them both to the Contessa at the same time, claiming they're in league, and becomes an enemy of the Cooper Gang from that point onwards. We learn at the end that she hated them from the start, and when given the order by Arpeggio to betray them, she was very pleased.
  • In Sly Cooper: Thieves in Time, Penelope starts to see herself as a rival towards Sly in regards to Bentley. Neither Sly nor Bentley are even aware of the sudden rivalry until the fourth chapter, where it turns out Penelope has betrayed them to Le Paradox, and is revealed to be a sociopath who just wants Bentley's skills to make billions of dollars in weapon designs and Take Over the World, while also planning to murder Sly (and Murray) out of jealousy and hatred. Unlike Carmelita and Neyla, it is left ambiguous whether Penelope did a Face–Heel Turn or was Evil All Along.
• Shadow from the Sonic the Hedgehog series becomes this to Sonic in his own game if you choose to join Black Doom by completing one of the dark missions in G.U.N. Fortress, Black Comet, or Final Haunt. In the latter case, Shadow switches sides at the last second specifically to be a dick to Sonic.
• Dirk in Suikoden Tierkreis is a mentor turned evil — not an Evil Mentor, but a formerly good mentor who succumbs to a combination of fear, suspicion, and jealousy after his proteges a): suddenly acquire magical powers they never worked to earn, and b): start to remember things he's certain never existed. He starts out just trying to snap them out of it but winds up barely coherent.
• Street Fighter: Sagat turned to crime and hatred after losing a fight to Ryu (and getting hideously scarred in the process — In his defense, Ryu did attack him with a cheap shot while under the influence of the Satsui No Hado). He turned good again at the end of Street Fighter Alpha 3.
• Strider 2 introduces Hien to the series, a fellow Strider and close comrade of Hiryu who shared several missions together. Hien's jealousy of his friend's seemingly unreachable ability, however, pushed him to side with the Grandmaster and cause the death of all Striders save Hiryu. Hien still considers Hiryu a friend and even tries to talk him out of fighting the Grandmaster, citing how futile his one-man crusade is, but Hiryu is determined to finish his mission and simply tells him to get serious next time they meet.
• Max in Temtem filled the typical rival role one would expect from a Pokémon Spiritual Successor, except it's later revealed that he's had a deep Inferiority Superiority Complex and resented the Player Character for years for being generally more talented than him. This leads to him joining the Belsoto Clan in exchange for powerful mons and doing everything he can to make the player's life hell.

Webcomics

• Pacific Rim: Amara: Yaozu and Sokolov are initially just racing rivals to Amara, but they turn villainous when they join up with the Mech-Czar and hurt Ada and Amara in the name of becoming the big stars of mech-racing.

Western Animation

• The Adventures of Jimmy Neutron, Boy Genius has an unusual case in the episode, "The N-Men". For this example, the titular character is the rival turned evil being angered by how Cindy keeps on overshadowing him. This eventually sets him off and he goes on a rampage. Ironically, the only person who can calm him down was Cindy, who he was originally mad at.
• Danny Phantom:
  • Jack Fenton and Vlad Masters, although the former is unaware of this case until the Grand Finale.
  • Tucker becomes this in "What You Want", going too far with his newly-acquired ghost powers and attempting to outshine Danny about it. He eventually gets better from it.
• In Trixie's second appearance on My Little Pony: Friendship Is Magic, she becomes this to Twilight under the influence of an Artifact of Doom.
• Snowball to the Brain in Pinky and the Brain; they might both want to take over the world, but all evidence suggests that the Brain will be basically a benevolent dictator where Snowball is more twisted.
• Peter Parker and Eddie Brock in The Spectacular Spider-Man were childhood friends, but over the course of the series, they drift further apart, as Eddie's grudge becomes greater, leading to their destined battle as Spider-Man and Venom.
• Splinter (Hamato Yoshi) and the Shredder (Oroku Saki) as seen in the 2012 Teenage Mutant Ninja Turtles. They were once good friends until they both fell in love with the same woman, Tang Shen. Their rivalry for her love soon turned into hatred (along with the revelation that Saki was adopted by his original clan's rivals), which ultimately killed Shen and Splinter's infant daughter. Though it later turns out that Saki had actually kidnapped and adopted Miwa, now renamed Karai, because he wanted the child of the woman he loved to be his.
• In Transformers: Prime Optimus and Megatron were once friends (hardly rivals) as Orion Pax and Megatronus while they worked together to progress civil rights on Cybertron. It didn't end well. Optimus still thinks he can bring his old friend back until towards the end of the first season. Megatron ultimately does have a Heel Realization in the Grand Finale Big Damn Movie, however, and while he and Optimus don't become friends again Prime is willing to let Megatron go into self-imposed exile without a fuss.

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