"Your enemy knows nothing about you
And he's got no way to get inIt's often the person you least expect. The Hero is looking for answers, beating up bikers, paying off informants and searching through the Great Big Library of Everything. His best friend and partner pleads with him to stop, it won't bring "her" back, and it just puts him in danger. Yet still the hero persists. A few acts later, he's getting beat on by the Giant Mook, it looks like it's all going to fade to black when... his partner shows up, gun in hand! Wait, why is he pointing the tranquilizer gun at hi— When he wakes up, the friend is terribly distraught. Says he tried to get him to stop, that he warned him what would happen. Saving him is out of his hands now, it's all on his head. Wait, what? The best friend has been in league with (or is) the Big Bad behind the whole plot. However, they genuinely like the hero and would rather he live a long and happy life. He might try a Circling Monologue to bring him onboard, but chances are he already knows the hero's moral code is such that he'd just be wasting both their time by doing it. Still, he just might try, for old time's sake. Compounding matters, he's usually a Straw Traitor to some horrible ideal, is either directly or indirectly responsible for much of the hero's recent suffering, and/or was covering it up. Compare Evil Former Friend and Evil Mentor. Contrast Friendly Enemy and Living with the Villain. Not to be confused with another type of big bad friend. If the hero is being chummy with the Big Bad, that's Go-Karting with Bowser. Evil All Along is for anyone who turns out to be evil, not just friends. Related to They Were Holding You Back. This is a Spoiler Trope, so beware.
But the way your heart is made to bleed
Is by your bosom friend"
But the way your heart is made to bleed
Is by your bosom friend"
— Blind Willie Davis, "Your Enemy Cannot Harm You"
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Anime and Manga
- All over the place in Attack on Titan. Eren learns that Annie Leonhart, the girl that taught him how to fight, is really the Female Titan responsible for slaughtering his squad mates. Not long after that, he learns that meek Bertolt Hoover and Team Dad Reiner Braun were the Colossal Titan and Armored Titan all along. And therefore, indirectly responsible for a good majority of the death in the series. To say he's less than thrilled is an understatement. For an extra twisting of the proverbial knife, all are presented as sympathetic and genuine in their attachment to the people they've betrayed.
- In Code Geass, Lelouch and Suzaku have this both ways. Suzaku is The Empire's Ace Pilot, and Lelouch is the Rebel Leader. Both are shown as sympathetic characters.
- At one point in Death Note, L, who suspects Light of being Kira by then, says he would be disappointed if Light turned out to be Kira because Light's the best friend he's ever had. It's especially heartbreaking because the audience has known from the beginning that Light is indeed Kira. Word of God says that he was probably lying. However, Matsuda wasn't — in fact, in Matsuda's case it was arguably worse: Light had been deceiving him for five years straight by the time the finale comes up and he tries to have Matsuda murdered. It's next to no wonder that poor Matsuda snaps massively in the end... and shoots Light several times while screaming and crying.
- In Devilman, Akira's best friend Ryo Asuka, the guy who got him into the whole horrible mess, turns out to be Satan.
- Fairy Tail has the Black Wizard Zeref as this to Mavis Vermillion. It was already confirmed in Chapter 340 of the manga that they knew each other (as fans had already suspected), but it wasn't until Fairy Tail Zero began that we find out how they knew each other; Mavis recognized his Ankhseram Black Magic and called it by name, and showed Zeref the first bit of genuine kindness he'd experienced in centuries, if not ever, to the point where Zeref agreed to teach Fairy Tail's founding members the magic they needed to defeat Blue Skull, making him indirectly responsible for Fairy Tail's very existence as a magic guild. Zeref later called this his 'most precious memory.' Even in the present, Mavis still clearly feels bad for the guy, but acknowledges him as the grave threat that he is. Even more tragically, they fell in love with one another after they realized they were both immortal, but Zeref's Curse killed her after their first and only kiss, and it's heavily implied Zeref's current desire to obtain Lumen Histoire, Mavis's body trapped in crystal, is motivated partially out of this love.
- In one story of Franken Fran, Fran's younger sister Veronica realizes that the only girl that had befriended with her in the private school where Fran has sent her is actually working for a criminal organization that is kidnapping students and selling them to pedophiles in foreign countries.
- In Is This a Zombie?, Eucliwood Hellscythe considered the King of Night to be her friend still, despite him unleashing a lot of megalo (demons) into the city to harm people and her new friends. He wanted to die, since he became an immortal zombie to serve her, but she wouldn't do it.
- In season 2, Nene, implied to be the strongest fighter in the underworld, is seen eating and drinking with Chris, the current Big Bad, and implied to be the strongest magical girl, who had fought each other before in the past.
- Freesia from the second season of Jubei-chan was a very calculating Dark Magical Girl who had wormed her way into Jiyu's home (and bed). When Freesia finally reveals herself later in the series, she shatters Jiyu's mind, sends her wounded off a cliff, and turns her father against her.
- In the anime of Kenichi: The Mightiest Disciple, the final boss of Ragnarok that Kenichi faces is Odin/Ryuto Asamiya, Kenichi's Forgotten Childhood Friend. True to being an Authority Equals Asskicking figure, it takes Kenichi a few episodes to finally take him down.
- As of chapter 117 of Medaka Box, Zenkichi joins the Flask Plan to teach Medaka the value of failure.
- In a filler arc, Naruto learns that the old man he often ate with at the ramen shop is actually a ninja from a village that had been destroyed, who seeks revenge against the Leaf Village. Interestingly enough, his friendship with Naruto actually was genuine, and he replaced the deadly explosive tags across the village with harmless ones, intending it as a scavenger hunt similar to the games he played with his son.
- Near the end of the series, Sasuke becomes this: after thwarting Madara Uchiha's plan to take over the world with a superpowerful genjutsu, Sasuke reveals that he plans to kill the Kages, trap the tailed beasts in satellites, and start a revolution and taking over the world himself.
- This is actually most of the premise for Saint Seiya: The Lost Canvas. The main character's best friend, Alone, becomes the host of the evil god, Hades. As one of Athena's saints, our hero must fight against his best friend.
- Alone means "Halo" in Italian (the setting of the story). The meaning in english is possibly intentional.
- After Arachnophobia's arc in Soul Eater, it turns out that Justin Law had gone through the first phase of this, but afterwards... well, turns out that Law worships Asura, not Shinigami-sama, is an extreme misogynist, likes to be playing Ho Yay with his longtime apparent enemy, and more than likely helped set up Kid to be kidnapped by the arc's Big Bad Chessmaster. So, he subverted this while acting The Mole. He might still like Stein, though, because he did retreat before injuring him.
- As of chapter 96, Chrona is stepping up to the role too.
- The third-to-last episode of Star Driver reveals that Sugata is the long-absent Emperor of Glittering Crux.
- In StrikerS Sound Stage X of Lyrical Nanoha, the culprit behind the Mariage killings turns out to be Teana's partner Runessa; Teana seemed to get along well with her, offering her a permanent partnership position at the end of the case, and Runessa, despite being the Detective Mole, was touched by the offer.
- In Sword Art Online, Kirito eventually realizes that Heathcliff, head of the most successful guild in the game, is actually Kayaba Akihiko, the man who trapped them there in the first place.
Kirito: It always bugged me...something that any child knows. There's nothing more boring than watching someone else play an RPG.
- Tiger & Bunny: The Big Bad is Maverick, Barnaby's mentor/father figure who killed Barnaby's parents because they knew too much. He started out as a Well-Intentioned Extremist, his actions being a way to make NEXTs into heroes who are appreciated in society rather victims of Fantastic Racism.
- This trope also applies to Wolfwood in the Trigun anime. He turns against the villains shortly afteward, only to die in the process.
- Youko's Poisonous Friend Yuka Sugimoto in The Twelve Kingdoms becomes her rival to become the Queen of Kei. Though unlike others, she gets better and relinquishes her claim, returning to Hourai/Japan.
- Chisato Inoue from Vampire Princess Miyu turns out to be this. Subverted in that Chisato wasn't aware of it either until almost the end, when her once-sealed demonic powers starte coming to the surface and her brother Tokiya, a full-blooded Shinma, is killed. From then on, the at first oblivious Chisato embraces her position as the Apocalypse Maiden and faces Miyu head-on, wanting to avenge Tokiya's death...
- This happens to Spider-Man with alarming regularly. His friends and co-workers are guaranteed to either die, go mad, or both.
Comics 101: [T]he Jackal was merely the latest in a long tradition in Amazing Spider-Man in which nearly everyone in Peter Parker's life either becomes a villain or is related to a villain in one way or another. Need examples? First girlfriend Betty Brant? She married Ned Leeds, who eventually became the Hobgoblin. Schoolmate Liz Allen? Her brother was the Molten Man. JJJ? His son becomes the Man-Wolf. Peter Parker's parents? Turns out they were killed by the Red Skull. The list goes on and on (and on). In a world like this, one of Peter's college professors becoming a supervillain makes perfect sense.
- Hartigan in Sin City has one of these, his partner Bob, who shoots Hartigan in the back to keep him from killing Senator Roark's pedophile son. There are apparently no hard feelings on either side, and Bob gives Hartigan a lift back to town after he gets out of jail.
- Bob is later (or earlier, depending on your point of view) killed by a different partner, whom Ava Lord had dug her talons into.
- Maxwell Lord to the JLI. Despite killing Ted Kord in the build-up to Infinite Crisis, Max still views them as his friends and warns them to stay out of his way, even telling Booster Gold that killing Blue Beetle wasn't easy for him.
- Adrian Veidt in Watchmen is introduced as a former team member of the other second-generation characters, although no longer especially friendly with them, but is actually the Big Bad of the comic, plotting to commit a massacre in order to fake an alien invasion and unite humanity.
- In Zero Robert is Ginsberg Nova.
- In the Doctor Who (Titan) comics, the Squire, a companion of both the War and Eleventh Doctors, turns out to be a shapeshifting agent for the Volatix Cabal (a Dalek Renegade Splinter Faction) and the true Big Bad of the Eleventh Doctor Year Two arc.
- Grunnel in With Strings Attached. He genuinely likes the four and is fascinated by what they have to say about Earth. But when Brox comes up with a use for Paul that Grunnel knows Paul won't agree to, Grunnel quite readily backstabs the four to ensure Paul's participation in Brox's scheme. As he says to Ringo: " Brox is my friend. You are not my enemies. Do you understand the difference?" Yet he prevents Brox from killing George and Ringo because he likes them.
- Drew in the Hannah Montana fic "I Didn't Sign Up for This". She is quick to befriend Miley and dates Lilly but in the last chapter, she is revealed to be a murderous sociopath that cares about no one but herself.
- In the side stories to MGLN Crisis, it turns out that Racquel Benna/Zettin, the fruit vendor Fate knows was actually a scientist who worked alongside Precia and Scaglietti, creating a clone of Clyde Harlaown who served to impregnate Precia with Alicia. Racquel said she moved near Fate hoping to tell Fate the truth one day.
- Phoenix Wright himself to Mia Fey in the fangame Turnabout Of Courage.
- And to the opposite extent, Rhea Wits to Apollo Justice in Turnabout Substitution.
- The entire plot of the My Little Pony: Friendship Is Magic fanfic Inner Demons revolves around a prophecy that Twilight Sparkle will be consumed by her inner darkness and become Equestria's Evil Overlord. This happens within a matter of chapters, and the rest of the story is dedicated to her trying to kill the rest of the Mane 6, and them trying to fight and/or redeem her (until the climax, there's a bit of debate among them).
- As another Twilight Sparkle-related example, Pages Of Harmony, Twilight is driven by a desire to extract the Elements from her friends by capturing and murdering them in various ways specific to their Elements. Though much like Light in Death Note, she appears to believe she's doing it for the greater good, and her friends try to get through to her and get her to come to her senses. She doesn't listen.
- Another Twilight Sparkle-related example (these are popular, aren't they?). Death Note Equestria has her taking on the role of Light as Kira. She's so determined to defeat L and enforce her vision of justice on the world that she even goes so far as to engineer Rarity and Pinkie's death as part of her cover; she does have a few Villainous B.S.O.D. moments along the way, but that hasn't stopped her so far.
- In the Medaka Box fanfic World As Myth, Hanhaba Shiranui fills this role towards the Broadcast Club in general, and Zenkichi Hitoyoshi in particular.
- Friendship Is Magical Girls: Rainbow Dash and Lightning Dust were friends growing up; when Lightning returns to town, Rainbow is thrilled at the prospect of renewing their friendship. Unfortunately for her, Lightning is a member of the Shadowbolts (the main antagonists of the Loyalty Arc), and has no problem using their friendship to gain information that can be used against the mahoushoujo. When Lightning eventually outs herself as a Shadowbolt, Rainbow is pissed, and then depressed.
Films — Live-Action
- Sword Of The Assassin: Nguyen Vu's childhood friend, whom Vu believed to be a freedom fighter, was actually a power obsessed Bitch in Sheep's Clothing who planned on having the entire royal family murdered to cement his rise to power. In the end, Vu deemed him even worse than the current empress, a woman who ordered the execution of Vu's entire family.
- Happened at least twice to Indiana Jones - Elsa Schneider, who was obsessed with the Holy Grail enough to help the Nazis in The Last Crusade; and Mac working with Communists in The Kingdom of the Crystal Skull:
Mac: I'm a capitalist. And they pay.
- More than once to James Bond, though he ought to have expected it. The biggest example is Alec Trevelyan aka Janus from GoldenEye, who once was James's partner and best friend as well as Agent 006, but after faking his death becomes the Big Bad of the movie.
- The 37th Dolan in The Last Witch Hunter was supposed to be the hero's assistant but turns out to be working for the villain.
- The film of Max Payne had this happen with the father's old partner and Max's mentor, who turns out to be the villain.
- In Snake Eyes, the best friend of the detective protagonist sets his friend up to cover up the assassination of the Secretary of Defense at the stadium. He's a Well-Intentioned Extremist who cooperated with a group of military contractors because of a dispute about a military software system that might be dangerous, which the Secretary wanted to cancel.
- The villain in Sneakers. "I cannot kill my friend." [hands gun to mook] "Kill my friend."
- Mission: Impossible: The villain turns out to be Jim Phelps, Ethan's boss and friend.
- The Third Man. The protagonist is investigating the murder of his friend Harry Lime. It turns out that Harry Lime is alive and engaged in horrible crimes. He's the villain of the story.
- Strange Days. The killer turns out to be the protagonist's best friend.
- Minority Report: Lamar Burgess is a Well-Intentioned Extremist who tries to set up a Utopia that unfortunately involves a murder. He was also John Anderton's good friend until he was exposed.
- The Truman Show. Truman's "best friend" since childhood (who is really an actor) at one point appears to truly be listening to Truman's plight and confusion, almost seeming to really want to help his buddy understand the crap that's going on with his life. However, he allows himself to be instrumental in the biggest Mind Screw the studio pulls on Truman in bringing his "father" back from the grave. He later leads the hunt to capture Truman once he starts escaping. Earlier drafts and deleted scenes emphasized the actor being torn over doing such a thing to a man he had genuinely come to view as his best friend, and in these drafts he initially redeemed himself by intentionally looking the other way when locating Truman and allowing him to escape.
- Hot Fuzz. Danny Butterman, the cop Nicolas befriends is actually in on what is going on, but tries to keep him out of trouble, even going so far as faking his death. Considering that when Nick tries to explain, Danny immediately enters an extreme state of denial and then sends him back to London, it's possible that he was aware on some level, but subconsciously never connected the dots for the sake of his own psyche. When Nicholas returns to stop the NWA, though, he chooses to join him.
- Blood Work: Terry McCaleb's associate, Buddy, happens to be a Well-Intentioned Extremist and the serial killer he was searching for all the time.
- Happened to Hartigan at the beginning of his segment in Sin City, when his partner shoots him in the back to keep him from killing the bad guy. But, you know, he really ought to have seen it coming, what with the partner being played by Michael Madsen.
- Textbook example in the Samuel L. Jackson and Ed Harris film, Cleaner. Ed Harris is Sam's best friend that helps him but later betrays him.
- Subverted in Talladega Nights: The Ballad of Ricky Bobby. Ricky Bobby is betrayed by his best friend Cal, who steals his glory, his house and his wife. Despite this, Cal continues to call Ricky on the phone to chat and ask advice (for instance, asking where things are stored in Ricky's house). Ricky, out of force of habit, chats with him until he remembers that he is mad at Cal.
- In Last Action Hero's Movie Within A Movie, Cowboy Cop Jack Slater's buddy in the FBI, John Practice, turns out to work for Big Bad Vivaldi.
- The hero's partner, played by Kevin Pollock, in End of Days turns out to be in league with the villains.
- Street Kings. Detective Tom Ludlow's entire police unit is in on Washington's murder and have gone way too far in their corruption, keeping Ludlow in the dark because of his better morals. Capt. Wander (the prime mover in the whole operation) even admits at the end that despite ordering him killed, he loves Tom more than any of the other guys in their unit and unlike them he is irreplaceable for him. They say goodbye as family before Ludlow shoot his friend.
- In Motives, the lead protagonist is set up for a fall by his best friend. Why? To steal the protagonist wife.
- In Dark Blue, Jack Van Meter sets up Perry's murder, which fails when Bobby is killed instead.
- In Another 48 Hours, sequel to 48 Hrs., Jack's fellow detective, Ben Kehoe, is revealed as a big time drug dealer. The character had been used for some exposition in the first film and it was somewhat given away by having him slick back his hair and wearing a suit in the second.
- Elijah Price is the Big Bad of Unbreakable, which he reveals only when he and David are starting to become friends near the end. He sees life as the prototype of a story after becoming intrigued by the comics his mother gave him, so he killed hundreds of people in mass disasters over the years to find his antithesis, a real hero. He manipulates David over the course of the film to fill this archetype, not to save people, but to find meaning in his own life.
- In R.I.P.D. Hayes turns out to be a dead-o, and organizing the dead's plan to reconstruct the Staff of Jericho.
- In The Amazing Spider-Man 2, Harry Osborn turns out to be this in the end, angered at Peter for refusing to give him his blood so that his disease could be cured. Electro can also count.
- Captain America: The Winter Soldier: Despite the title, the Big Bad Friend is actually Pierce towards Nick Fury, not Bucky Barnes towards Steve Rogers.
- Senator Paine from Mr. Smith Goes to Washington admires Mr. Smith's idealism and doesn't want to see him ruined by the political machine that he ends up fighting, though not enough to come clean. Until the end, that is, when his conscience finally gets the better of him.
- Underground: Blacky's best friend Marko betrays him and becomes the Anti-Villain of the film.
- The Believers: Cal's closest friends turn out to be part of an evil cult that sacrifices children and want him to join them by offering up his own son.
- The Faculty: The Hive Queen that controls the alien parasites turns out to be the New Transfer Student Marybeth Louise Hutchinson, part of the student resistance group itself. Even they're shocked by this realization, for all how their Genre Savvy nature about how horror and alien movies work has helped them survive.
- Nightfall Series: Myra ends up developing a twisted, love-hate friendship with Prince Vladimir, to the point that he is even giving her tips on how to defeat him.
- Treasure Island: Long John Silver, Jim Hawkins's mentor figure and the local Magnificent Bastard, is probably the most famous example of this trope. So much that he manages to get away with it in the end.
- In Agatha Christie's Ordeal by Innocence, the former nanny is this to Philip Durrant, warning him to stop prying into the murder of his mother-in-law, which she committed on behalf of the victim's delinquent son. She murders Philip to cover her tracks.
- In Dragonlance, Kitiara in her final moments is mind raped when she discovers that her servant, Lord Soth intends to kill her and make her serve him as his banshee for all eternity.
- Robert Harris' Fatherland, where Xavier's old friend Max Jaeger turns out to be the source of the SS's inside information.
- Fidelias to Amara in the Codex Alera series. Not much of a spoiler, though, since his real allegiance is revealed within the first couple of chapters of the first book.
- In Tunnels, the Big Bad turns out to be the protagonist's little sister.
- In Sergey Lukyanenko's Rough Draft, the main character has just killed a powerful Functional who was trying to kill him. He then meets his friend but quickly realizes that he's one of them. The friend initially tries to help him but then nearly kills him. It gets weirder in the sequel, Final Draft, where the friend returns, explaining he was just scared. At the end, though, he challenges the main character to a duel.
- American Gods: One of Shadow's old friends, Low-Key Lyesmith from his stint in prison, is actually Mr. World/Loki. This becomes especially trying it involves Mr. Wednesday, he turned out to be working with Loki the entire time, working to manipulate both sides into a devastating war.
- In Aristoi, Zhenling was part of the Big Bad's plan to crack Gabriel's encryptions all along.
- In The Underland Chronicles, to all appearances, Henry's affection for his cousin and his offer to rule with her are sincere.
- The Thing in Tamora Pierce's Mastiff.
- Natalie to Lissa in Vampire Academy. She acts as a caring friend to her, while secretly killing animals, which Lissa cares for, messing with her mind and trying to get her captured by her dad.
- In books 5 and 6 of The Saga of Darren Shan, Darren's discovery and exposure of Kurda's treason plays out like this, although he really is more of a Well-Intentioned Extremist.
- Played straighter in book 9 with Steve Leonard, who... isn't.
- In Void City, one of the major antagonists is Roger, Eric's oldest friend and long-time business partner, who has secretly despised him and wanted to kill him for decades.
- Gaheris Rhade from Andromeda. However, "The Unconquerable Man" put a twist on it. Gaheris actually won the fight originally, but got frozen in time like Hunt did in the pilot. He eventually gets rescued by Beka and company, just like in the pilot. In fact, he lives through much of the series plot, though it plays out far differently. He tries to rebuild the Commonwealth to make up for the fact that his people slaughtered everything that moved after the Andromeda was lost, and were ultimately nowhere near the Warrior Poets he had thought. Tyr is killed by Rhade for betrayal, Perseid gets annihilated, and the universe is about to be ripped to shreds when Trance tells him there's another chance to fix it all. Rhade eventually agrees, uses said universe shredding phenomena to travel back in time and kill his previous self moments before he begins his mutiny, takes his uniform, and throws the fight with Dylan Hunt at the beginning of the pilot episode. Chronologically, the main series then follows. Does anyone have anything for a headache?
- Buffy the Vampire Slayer:
- In Season 9, Whistler is revealed to be working with Pearl and Nash.
- The Big Bad of Season 2, to whom the Anointed One and Spike & Drusilla both play Disc One Final Boss, ends up being Angel, having returned to his former self after losing his soul.
- In Season 3, Faith turns out to be The Dragon to Mayor Wilkins.
- In Joss Whedon's Dollhouse, lovable, loyal Boyd, the hero's friend, turns out to be the Big Bad.
- On season 4 of Angel, the Big Bad orchestrating the disappearance of the sun and master of the giant rock demon turns out to be Cordelia, although she's actually being controlled by a god.
- An inversion occurs in Battlestar Galactica. After Saul Tigh is outed as a Cylon, Adama accuses him of being one of these. Tigh himself however was more of a Poisonous Friend.
- Game of Thrones: Locke pretends to be a friend to Jon Snow starting from "Oathkeeper". He leads Jon to believe that he's just another recruit for the Night's Watch who bravely offered to accompany his party to track down and deal with the mutineers who killed Lord Commander Mormant and are tormenting the women at Craster's Keep. In reality, Locke is there to find and kill Bran and Rickon Stark, Jon's half-brothers, who immediately threaten the Boltons' claim on the North. He betrays Jon by preventing Jon from saving Bran and Rickon and may have planned to harm Jon himself — but Bran manages to kill Locke before he can — and Jon remains unaware of Locke's true intentions since Locke was killed before anything was revealed to him.
- The Big Bad of Season 6, to whom Crowley, Eve, and Raphael played Disc One Final Boss, is revealed to be Castiel, who has decided that to defeat Raphael and put Heaven on the right track, anything is acceptable - in this case, taking on a million souls. However, throughout nearly the entire season, he staunchly remains their friend, putting their safety ahead of his plans on multiple occasions and vehemently protecting them from Crowley, who would prefer to kill them. The Winchester boys do their best to stop Castiel throughout the final episodes of the season, while he continues to plead for them to accept him and his reasons for evil.
- In the final episode of Season 4, Ruby reveals to Sam that she had been collaborating with Lilith the whole time just as Lucifer rises.
- In Mighty Morphin' Power Rangers, Tommy plays with this, though he's just Brainwashed and Crazy himself.
- In Luther, the antagonist of the first series' final two episodes is DCI Ian Reed, Luther's friend and confidant, who is actually a Dirty Cop.
- Subverted in the episode The Great Game from Sherlock. When John appears to meet Sherlock at the pool, we (and Sherlock) assume that he's Moriarty. However, it's soon revealed that he is strapped to a bomb and the real Moriarty was just making him say lines that imply he is.
- In Jekyll Peter Syme turns out to be working against Jackman. And makes the argument that after so long pretending to be a friend they really are friends, even after betraying him.
- Mitsuzane Kureshima/Kamen Rider Ryugen from Kamen Rider Gaim is particularly tragic example. He made increasingly desperate and messed up attempts to protect his friends without every taking a single moment to think whether they want or need that, digging himself deeper with each move. Long story short, by the series' end he maimed, murdered or attempted to murder nearly half of the cast all because he thought he knows the best.
- 24 plays this straight with Nina Meyers and plays with it for Tony Almeida. While Nina was The Mole working for the first season's Big Bad, Tony through his own warped sense of justice is aiding the seventh season's Big Bad to get him to trust him so he can kill him in revenge for being the mastermind behind the plot that lead to the death of his family.
- Since we rarely get much of an insight into the personal lives of the detectives and prosecutors who appear on the numerous Law & Order series, it's almost a certain bet that whenever an old friend of one of the characters shows up, it will turn out that they've become one of these.
- This describes Lex Luthor for the first four seasons or so of Smallville, and intermittently afterward. Notable in that this isn't presented as a twist, but as a continuing theme throughout the series — he legitimately likes the protagonists, he just sees their demands that he stop digging up their secrets as a requirement to tell them he's stopped in the interest of courtesy (rather than a moral need to actually stop).
- Dr. Hannibal Lecter to Will Graham (and to a lesser extent, Jack Crawford) in Hannibal. In a departure from the source material, where Graham never met Hannibal before exposing him as the "Chesapeake Ripper" and arresting him, Hannibal is here referred to Graham as his FBI-mandated psychiatrist. He becomes friends with Graham and Crawford and lends his medical and psychological expertise to the FBI's Behavioral Sciences unit, the group out to catch the Chesapeake Ripper, while Gaslighting Graham for his own amusement and other ends.
Hannibal: I was hoping you and I wouldn't have to say goodbye: nothing seen, nor said.Alana Bloom: Stop! I was so blind.Hannibal: In your defense, I worked very hard to blind you.
- By the end of season one, Graham realises that Hannibal is this trope, but by then he's been manipulated into near-insanity and framed for a string of Hannibal's murders, destroying his credibility. In season two, Hannibal exploits Jack's emotional vulnerability over his wife's cancer and seduces Alana; he grievously injures them and Will in the finale, making him this for the entire main cast.
- Agents of S.H.I.E.L.D.: Near the end of the first season, it's revealed that The Clairvoyant is actually Coulson's best friend, Agent Garrett. And things get even worse when it turns out that Ward is working for him as well.
- In The Flash (2014), it is revealed at the end of the first episode (to the audience, not the characters) that Team Dad Genius Cripple Harrison Wells is not only not paralysed, but that he has a secret room in his lab with an AI that shows him the future, and that he's been keeping an eye on Barry for a very long time. He only gets more Ambiguously Evil from there, culminating in The Reveal that he is the Reverse-Flash, Flash's archenemy who killed his mother.
- Forbrydelsen did this in all three seasons. In the first season, the murderer turns out to be Vagn, the best friend of the main victim's father. In the second season, Lund's new partner Strange proves to be the killer. And in the final season, the main villain is Reinhardt, the business partner and close friend of the kidnapped girl's father (although the kidnapping was by the vengeful father of the girl who Reinhardt raped and killed).
- Penny Dreadful: In the first season finale, it's revealed that Mina Murray is in fact a willful servant of the vampires, and has been acting as bait to lure Vanessa into their clutches.
- In Season 2, the team turns to Professor Lyle to help them translate the Verbis Diablo, unaware that he's actually working for the witch coven they're fighting. To his credit, however, Lyle is being blackmailed into the situation, is clearly uncomfortable with it, and tries to subtly defy the witches and warn the heroes on several occasions. When Sir Malcolm is taken prisoner by the witches at the end of the season, Lyle finally confesses his treachery to the team and helps them storm the witches' castle to rescue him, even managing to personally kill one of the witches.
- In the second BIONICLE movie, Turaga Dume starts out as a trusted friend and city leader to both Toa Lhikan and Toa Vakama, even if he DOES act a little strangely. Turns out he's the one who ordered the rest of Lhikan's team to be killed off years ago and for ex-Toa Nidhiki and Krekka to capture him as well, even managing to capture and imprison half of Vakama's team in the Coliseum and generally causing mass chaos and destruction all around. And then it turns out that Dume is not Dume at all, but rather Makuta disguised as Dume, who has been in stasis for years. Even better, before this, Makuta was a trusted guardian of their home island, meaning there are two examples of this trope in one movie.
- "Your Enemy Cannot Harm You" by Blind Willie Davis is about how your enemies don't know enough about you to hurt you as deeply as a traitorous friend.
- During the summer of 1991 The Ultimate Warrior turned to his friend Jake "The Snake" Roberts for help in learning how to defeat The Undertaker. Roberts explained that after passing three tests, Warrior would have the "knowledge of the dark side" to defeat Undertaker. These tests included Warrior being locked inside a coffin and being buried alive in dirt. The final test was Warrior walking through a room full of live snakes to reach a chest containing "the answer". Warrior opened the chest, only to be immediately bitten by a King Cobra. As Warrior weakened from the effects of the snakebite, Roberts was joined by The Undertaker and Paul Bearer, revealing the three were working together all along. Jake Robert's last statement to The Ultimate Warrior was "Never trust a snake".
- Flipped around in Dragon Age: Origins: The villain Loghain thinks that his king and son in law is a Big Bad Friend who is selling out the kingdom to the same empire that his father and Loghain expelled from the country just one generation ago. Thinking the king has already made his Face–Heel Turn and become The Quisling, he betrays him and takes control of the kingdom himself.
- Return to Ostagar reveals that the king was indeed planning to divorce Loghain's daughter Anora and marry the Empress of Orlais had he survived the battle, which if Loghain is a party member at the time has him both vindicated and furious that he was right all along.
- Subverted again in Dragon Age II, where Cassandra is convinced that Varric's friend Hawke was the Big Bad responsible for everything and went to Kirkwall specifically to start the Mage-Templar War that is currently sweeping Thedas, when in reality, they were simply the Right Man in the Wrong Place and were swept up in events far outside of their control. Played straight with Anders, however, who blows up the Kirkwall Chantry, killing scores of innocents, to incite a mage rebellion, ultimately leading to said war.
- And then Dragon Age: Inquisition gives us Solas, a.k.a. the elven god of rebellion Fen'Harel. Not only was he indirectly responsible for the Breach, he has been manipulating the Inquisition the entire time, and is actually planning to destroy the Veil, merging Thedas and the Fade, which would most likely kill every living being on the planet.
- In Tales of Symphonia, Mithos is quick to befriend the party once they meet him, and he becomes especially close with Genis. Once Genis finds out that his "friend" isn't just an enemy, but the leader of Cruxis and Big Bad of the game, he reveals that he had his suspicions, but didn't want it to be true, and spends much of the rest of the game struggling with his feelings of betrayal, but thinking of Mithos as a friend on some level..
- Kratos is set up as another such case. Initially, the character doesn't seem all that close to anyone in the group, having supposedly joined only for the money (which is actually a lie), but gradually becomes something of a mentor to Lloyd, if fairly cynical. The group takes it hard when they realize Kratos has betrayed them, but late in the game, it turns out that he was Good All Along, and Lloyd forgives Kratos after defeating him in a final duel.
- Special Agent Kato the third and final Big Bad in Shadow Hearts: Covenant, doesn't let a little thing like wanting to destroy the world ruin the good friendship he has with Yuri. He even encourages the heroes to stop him if they truly believe they've got the right moral standpoint compared to his.
- Joshua in The World Ends with You. You actually have him as a member of your party for 1/3 of the game, as well as a cutscene that starts out short but is slowly revealed (an attempt to confuse the player as to whether Neku's killer was him or the Reaper, Minamimoto). The game switches itself up on you: It intentionally makes you suspect that Joshua did it, then reveals it to be Minamimoto with some rather convincing evidence, even so far as to make you think that Minamimoto could be the final boss, especially after he revives himself. Then, the end of the game does a 180 and reveals that Joshua was not only the killer, but the Composer of the game as well: He killed Neku (who could use any pin) so that Neku could take his place in the Game that would determine Shibuya's fate.
- Metal Gear
- The Boss in Metal Gear Solid 3: Snake Eater, before defecting, was Naked Snake's mentor and one of his closest friends. She celebrates her Face–Heel Turn by beating him up and stealing his rescued hostage. It was a ruse to make Volgin trust her and Snake wasn't in on it.
- The same goes for Naked Snake as Big Boss with the chronologically later Metal Gear as the commander of the young Solid Snake.
- Vossler from Final Fantasy XII fights alongside you for a chunk of the game, but sells you out to the Archadian Empire afterwards on the belief that it would be better to surrender to stop the bloodshed instead of continuing a seemingly fruitless rebellion. He's immediately given the Straw Traitor treatment, fights you as a boss later on, and then dies dramatically on an exploding warship.
- Each of the Sworn Six of Paladia from Final Fantasy Brave Exvius is directly linked to the party in some way, but none more so than Veritas of the Dark, who is heavily hinted to be Sir Raegan, Rain's father and Lasswell's adoptive father.
- The Neverwinter Nights mod series The Bastard Of Kosigan has a couple. That group of mostly-nice witches you were helping out in the first module? Oops, they were manipulating you into helping them summon an ancient demon with which to wipe the world clean of civilization and start over with magic-users in control. Your lover in the second module? Whoops, she was the mastermind behind every assassination attempt on you or your family for the entire story so far. Both cases give you the chance to join them when their plots are revealed, which due to the story's Grey and Grey Morality, isn't that far off the 'good guys' plots.
- In Dungeon Siege 2, the Azurite Scholar that has been helping you throughout the game turns out to be the Overmage of the Cinbri, who has been manipulating both you and the Big Bad in order to reshape Aranna in his image.
- Fasti, who is actually Mobius, is the Big Bad of Agarest Senki 2. Until he does The Reveal, he was the resident Smart Guy.
- In EarthBound, Pokey claims that Ness is his best friend, and you can tell a cop that you're both friends, too... until he does a Face–Heel Turn. Though, that would make him The Dragon Friend... Until MOTHER 3. In that game, it shows that he really did consider Ness a friend; he cherishes the latter's weapon, the "Friend's Yo-Yo" and keeps a shrine to him in his headquarters.
- In RosenkreuzStilette, Iris is considered like a kid sister to the rest of RKS, including Tia. What they don't know is that she's really the Big Bad who's making RKS fight against the Holy Empire For the Evulz. She eventually reveals to Tia who she really was and the real reasons for the war, and that she really did all that for both said reason and to become god of the world. That's where none of RKS trusts her anymore.
- At the end of Beyond Divinity, its revealed that your only ally throughout the game, the unnamed Death Knight, is actually, Damian, the Big Bad of the Divinity series.
- Citan Uzuki from Xenogears isn't only a Big Bad Friend to Fei, he's Fei's mentor!.
- In the Lufia series, a common plot element is a certain character being Erim, the Sinistral of Death. In Lufia & The Fortress of Doom it was Lufia herself, in Lufia II: Rise of the Sinistrals it was Iris, and in Lufia: The Legend Returns it was Seena. Often, this character is not even aware of their true identity.
- Happens several times in the Grand Theft Auto series:
- In Grand Theft Auto: Vice City, Lance Vance sells out Tommy Vercetti to Liberty City mafioso Sonny Forelli in the final mission out of opportunism because he felt he was being sidelined by Tommy in the Vercetti criminal empire.
- In Grand Theft Auto: San Andreas, Big Smoke and Ryder betray the Johnsons to corrupt police officers Frank Tenpenny and Eddie Pulaski to get rich off the drug trade.
- Billy Grey in Grand Theft Auto IV: The Lost and Damned. He ultimately decides to sell out the entire Lost MC for his freedom; however, Johnny Klebitz infiltrates the prison and personally executes Billy before he can testify.
- Faize in Star Ocean: The Last Hope after a Heroic B.S.O.D. sets down the path of darkness.
- Space Pirates and Zombies has Don who turns out was a zombie leader/commander all along, and was leading you to the core to unleash the zombies.
- Pavel in Metro: Last Light is Artyom's travel companion for a major part of the game and the two end up saving each other's life several times before they finally make it back to a civilized station where they are safe to relax and stock up on supplies before they each make their way to their respective homes. Over a farewell meal, he tells Artyom that he's not just forced to be a soldier for the Communists, but actually believes in their principles. At that moment two communist officers appear behind him and it turns out that he's not just a simple scout, but a Major who was tasked to capture Artyom and just happened to end up in the same Nazi prison after his team was killed. And he just had been spiking your drinks.
- Livia in Alpha Prime. At the end, it's revealed that they're not just The Mole, but were the Company's agent that orchestrated the plot in the first place. This also leads into the bad guys winning.
- The Final Boss of Knights of the Old Republic II: The Sith Lords is one of your party members and also the person who's been mentoring and advising the player character throughout the game. Whether she actually qualifies as Evil All Along, though, is left up to the player to decide.
- There's a prominent fan-theory that The Phone Guy in Five Nights at Freddy's, is the unnamed Serial Killer in the game's backstory who murdered a group of children, whose murders are implied to be the reason why the titular pizzeria's animatronics are murderous.
- For the first half or so of Tony Hawk's Underground, it's simply a story of two guys (or a guy and a gal) from New Jersey trying to make it big as pro skaters. However after the pair arrive in Hawaii, the Player Character decides to pull off a big stunt by tricking over a hovering helicopter and the character's friend, Eric Sparrow, is on filming duty. The main character successfully pulls off their amazing feat but Eric seizes the tape and passes it off as his own work, taking all the fame that would have gone to the player character. The rest of the game is spent trying to catch up to Eric and pay him back for screwing your character over.
- Halo 5: Guardians: Cortana is back and evil but still very devoted to Master Chief. The difference in her warm encouragement to John 117 and bitter hostility to the new Deuteragonist Locke is very noticeable.
- It turns out that the Parkour Killer in Mirror's Edge is Faith's best friend Celeste, who believes the Runner's days are numbered and is fine with helping the police capture all her old Runner buddies to save her own sorry ass.
- Anachronox: In the end, Grumpos, the second character in your party, looks like he's going to destroy the key to open the portal, but instead reveals he's with the bad guys the whole time and opens the portal for them.
- K.O.L.M.: In the second game Father, who'd seemed to be ally, turns out to have been working with Mother the whole time and tosses Robbie aside when he succeeds in bringing Sister to him.
- Persona 5: Goro Akechi, one of the characters the Protagonist befriends over the course of the game, turns out to be The Heavy for the bad guys, and the one ultimately responsible for the formation of The Conspiracy.
- The Testament of Sherlock Holmes implies that Sherlock Holmes is this to Watson, as it drops hints that the famous detective might be the mastermind of the murders committed throughout the game. Watson's deteriorating friendship with Holmes is an ongoing plotline. Holmes is innocent, of course, but he's doing it deliberately. Moriarty is framing Holmes for the crimes, and Homes is intentionally acting suspicious to keep Moriarty's attention off of Watson.
- Final Fantasy XIV: Thancred, one of the Scions of the Seventh Dawn, and the player's first ally if they started off in Ul'dah, was secretly possessed by the game's big bad, Lahabrea, an immortal aethereal being who possesses mortal hosts to bring about the resurrection of his dark god. It's implied that Thancred was under Lahabrea's control since long before the player met him.
- Nocturne: Rebirth has Khaos, who Reviel considers a friend despite the former scheming against him and trying to destroy/recreate the world, which is why he tries to get his friend to pull a Heel–Face Turn. Unfortunately, the Big Bad ends up committing suicide upon defeat because he was that desperate to enact his plan. The Dragon, Shylphiel, states that Khaos was likewise fond of Reviel, Luna, and Ristill despite his antagonism.
- The Legend of Heroes: Trails of Cold Steel has Crow. Throughout the game, Class VII has been antagonistic against a group of terrorists called the "Imperial Liberation Front" whose leader is a man called "C". Turns out that said leader is Crow whose room is just across Rean's room. He doesn't give out his reasons until the second game as to why he did his terrorism acts.
- Ace Attorney:
- We don't actually see the moment of revelation for Phoenix Wright, but Kristoph Gavin is the one who set him up to be disbarred and dishonored in Apollo Justice: Ace Attorney. He then spends seven years pretending to be his dearest friend, and the only person who objected to his punishment until Phoenix finally takes him down.
- In Investigations, Shi-Long Lang is shocked to discover that Byrne Faraday's killer and a key member of the smuggling ring is his assistant Shih-na.
- Calisto Yew serves as one to Byrne Faraday and Tyrell Badd, her accomplices in the Yatagarasu, when she betrays and kills Byrne, due to being The Mole for the smuggling ring the Yatagarasu is fighting.
- Implied by Apollo in the last case of Dual Destinies, when he states that Prosecutor Blackquill seems torn after The Reveal of Bobby Fulbright's true identity, as the two of them were partners. The previous cases also give the feeling that there was a strong, if unusual, friendship between them.
- Through cases 4 and 5 of Dual Destinies, Apollo wonders if his friend and co-worker Athena Cykes has killed his childhood friend Clay Terran. His lead is that he senses with his Hyper Awareness that Athena is hiding something from him, which is rare for her. Subverted: the killer was an enemy to Athena as well and she was just another victim of the whole ordeal as she's framed for Clay's murder (and Athena's mother's murder too).
- Dangan Ronpa is a big fan of this. Since every case is composed by a murder committed by one of the people who you had to live for a little while, while most case end up showing the murderer as sympathetic in their motives, some times they do come off as cold blooded killers, such as Celestia, who killed Hifumi and Ishimaru to get out of the school with the money offered by Monokuma, Mikan, who killed Ibuki and Hiyoko after regaining her memories as a member of Ultimate Despair and Nagito, who not only essentially caused the first murder sets up his own death to be unsolvable, on a try to get everyone besides Chiaki killed. After Celestia's execution, Makoto notes that since the culprit killed his friends, he can't pity her, but acknowledges once thinking of her as a friend.
- The sequel takes it even further: The last case reveals that Hinata and everybody else but Chiaki are the Remnants of Despair, a group of Ultimate Despair that served directly under Junko and are trying to destroy the world, though none of them have memories of that.
- Chiaki is a subversion, as even though she was the traitor, she was working for the Future Foundation, who was trying to help them. During the aforementioned incident in which she is set up as Nagito's killer, she does everything she can to ensure that she's convicted (and executed) for it, even though she's unable to actually come out and reveal herself as the "traitor".
- In Nine Hours, Nine Persons, Nine Doors, Zero has kidnapped nine people and is forcing them to play a Deadly Game. What's Zero's identity? Akane Kurashiki, the protagonist's childhood friend who has been playing along with him through the game pretending to be an innocent victim of the ordeal.
- Old school Japanese PC/NES adventure game The Portopia Serial Murder Case has this as The Reveal, as the titular killer turns out to be Yasuhiro "Yasu" Mano, who is not only the main character's partner but also the single most unlikely suspect as he is with you throughout the entire game, executing the commands of the unseen protagonist. The shock factor was so high that nowadays the phrase "Yasu is the culprit" is something of a meme amongst old fans. This twist is so well-known that it's been given Shout Outs in Haruhi-chan, Episode 7 of Umineko: When They Cry, and Chapter 3 of Dangan Ronpa.
- In Sluggy Freelance Torg believes Riff is one of these following the "Hereti-Corp freelancer" revelation, though it's more a case of "unwitting stooge." Played straight with Sam during the "Vampires" Story Arc.
- Subverted in Brawl in the Family's "Cocoon Academy" arc. Not only is it not Dedede's Start of Darkness, but it turns out to be Meta Knight's origin story instead of Kirby's.
- Defied in Perfect Kirby with Bill, the Big Bad of the first installment. Kirby considers Bill an annoyance, and while he is surprised by Bill being the Xbox smuggler, he rejects Bill's claim that they're friends.
Kirby: Bill, we've only known each other since you moved in, two weeks ago!
Bill: When did this happen, three weeks ago?
- Kevin in Tribe Twelve is secretly The Observer. No one is happy to hear it.
- Todd Ianuzzi from Beavis And Butthead is a variation of this trope. Most of the time is associated or pretends to be a friend of Beavis and Butt-Head, but he is really an Ungrateful Bastard and a bully who enjoys committing crimes. However, Beavis and Butt-Head think he is "cool".
- In Avatar: The Last Airbender, Fire Lord Sozin was best friends with Avatar Roku. the two became distant due to Roku's duties as the Avatar and Sozin's plans for conquest, and Sozin betrayed him as soon as he had the chance. Notably, however, on his deathbed Sozin took the time to reflect on his actions and realized that he did regret what he had done, only to bitterly note it was far too late for apologies to make things right.
- Sequel series The Legend of Korra has Varrick for Bolin. He did betray him and his friends, intended to use Unalaq's plan for his own selfish benefit, but Bolin still respected him and was still willing to accept his help against their real enemies. This seemed to become a more legitimate, trustworthy friendship as the series progressed however.
- Danny Phantom: Danny's Arch-Enemy Vlad Masters is this to Danny's father Jack, who was his best friend in college. Not that Vlad makes much of an effort to hide how much he hates Jack in the present (which Jack remains oblivious to), except when he wants something from him, but he does a good job of convincing everyone other than Danny and co. that he's not evil. At least until the Grand Finale. When Jack found out he'd been played he was...not happy.
- South Park:
- In "The Mystery of the Urinal Deuce", we find out that it was Stan Marsh who put the dookie in the urinal. Though it was terrorists who caused 9/11. The "9/11 Truth" movement is a Government Conspiracy in order to keep the "retarded one fourth of America" in line through fear.
- In several other episodes, Eric Cartman. Though something of a parody, because his friends know he's not to be trusted—-it's just that somehow, he usually winds up convincing one or more of them to believe him anyway, just to stab them in the back. Further parodied/lampshaded in the Wal-Mart episode, where Kyle Broflovski keeps pointing this out, though Cartman still seems to think they all believe him.