Big Bad Friend

"Hartigan: Then there's thunder from behind me and lightning bolts punching holes through my chest. I guess I won't be having that steak I was looking forward to, after all. My last day on the job. Hell of a way to start my retirement.

Bob: Damn it, Hartigan, I warned you.

Hartigan: Hell of a way to end a partnership."

- Sin City: That Yellow Bastard

The Hero is looking for answers, beating up bikers, paying off informants and searching through the Library of Babel. 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 heroes recent suffering, and/or was covering it up.

Contrast Friendly Enemy and Living With the Villain. Not to be confused with another type of big bad friend. 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.

Anime and Manga

 * 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.
 * However, Word of God says that he was 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.
 * 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.
 * This trope also applies to in the Trigun anime.
 * 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.
 * After Arachnophobia's arc in Soul Eater, it turns out that had gone through the first phase of this, but afterwards... well,  So, he subverted this while acting The Mole. He might still like Stein, though, because.
 * As of chapter 96,  is stepping up to the role too.
 * Jin to Joe in Innocent Venus.
 * In Code Geass, Lelouch and Suzaku, as Suzaku is in league with the Emperor himself for a while.
 * Youko's Poisonous Friend Yuka Sugimoto in The Twelve Kingdoms.
 * Cowboy Bebop: Jet confronts one of these in "Black Dog Serenade".
 * In one story of Franken Fran, Fran's younger sister Veronica
 * In Devilman,
 * The third-to-last episode of Star Driver reveals that is the.
 * As of chapter 117 of Medaka Box, to teach Medaka the value of failure.
 * In Kore wa Zombie Desu Ka, 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.
 * In Season 2,

Comic Books

 * Hartigan in Sin City has one of those.
 * Who 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 Blue Beetle 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.
 * in Watchmen.

Fan Works

 * in With Strings Attached. He genuinely likes the four and is fascinated by what they have to say about Earth. But when  comes up with a use for Paul that   knows Paul won't agree to,   quite readily backstabs the four to ensure Paul's participation in  's scheme. As he says to Ringo: “  is my friend. You are not my enemies. Do you understand the difference?” Yet he prevents   from killing George and Ringo because he likes them.
 * in the Hannah Montana I Didn't Sign Up for This. She is quick to befriend Miley and even dates Lilly but in the last chapter, she is revealed to be a murderous sociopath that cares about no one but herself.

Films -- Live-Action

 * Happened at least twice to Indiana Jones.
 * More than once to James Bond, though he ought to have expected it.
 * The film of Max Payne had this happen with the father's old partner and Max's mentor.
 * The film Rogue features this as part of it's double-twist ending.
 * Happened in Snake Eyes, the best friend being a Well-Intentioned Extremist.
 * The villain in Sneakers.
 * Mission Impossible III
 * Harry Lime from The Third Man.
 * Strange Days.
 * 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 emphasised 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. The cop Nicolas Angel 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. (This also makes him a practioner of Obfuscating Stupidity.) He's brought around by The Power of Friendship in the end.
 * "In on it" is wrong, or at least overly simplified. Danny knew that there was . However, he didn't know that  . It's not clear whether he thought the deaths attributed to accidents were elaborate extremely sophisticated stunts, or whether he just never connected them to the conspiracy, but in either case the stupidity is probably not obfuscation.
 * Obfuscating Stupidity isn't always pure obfuscating. It's sometimes self-imposed flanderization, y'know.
 * Considering that when Nick forces him to realise the truth, Danny immediately enters an extreme state of denial, its possible that he was aware on some level, but subconsciously never connected the dots for the sake of his own psyche.
 * Bloodwork: A friend of the hero is quite the Well-Intentioned Extremist.
 * 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.
 * The Julia Roberts/Nick Nolte rom-thriller I Love Trouble.
 * Textbook example in the Samuel L Jackson and Ed Harris film, Cleaner. HINT: Ed Harris is Sam's best friend the 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 even 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.
 * As with most tropes in the film, both parodied and lampshaded. The Kid recognizes Practice as the man who "killed Mozart", F. Murray Abraham
 * The Partner, played by Kevin Pollock, in End of Days.
 * Edward (not Edmund, like in real life) is this to Detective Harris in Kemper: The CoEd Killer.
 * Detective Ludlow's entire police unit in Street Kings, Wander (his boss and best friend) especially.

Literature

 * Long John Silver is probably the most famous example of this trope.
 * In Agatha Christie's Ordeal by Innocence,
 * 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.
 * Of course, this being Kitiara, the surprise isn't that Soth is evil, but that he'd betray her. For his part, although he knows it's entirely selfish, Soth does what he does purely out of love for Kitiara. It's a big bad dysfunctional family they've got going on.
 * Robert Harris' Fatherland, where 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.
 * Every Dan Brown novel features this trope where the friend or trustworthy boss turns out to be the Big Bad
 * in Angels and Demons.
 * in Digital Fortress.
 * in Deception Point.
 * in The Da Vinci Code..
 * in The Lost Symbol.
 * Red Seas Under Red Skies begins with a flash-forward scene where best friends Locke and Jean are in a standoff with two assassins, all four of them armed with crossbows. With some reluctance, Jean suddenly turns on Locke, claiming to be in league with the assassins' employer and demanding he hand over his weapon.
 * In Tunnels, the Big Bad turns out to be.
 * 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:

Live Action TV

 * Gaheris Rhade from Andromeda. However, the episode "The Unconquerable Man" put one hell of a twist on it.  Chronologically, the main series then follows. On a related note, does anyone have anything for a headache?
 * In Joss Whedon's Dollhouse, lovable, loyal  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.
 * An inversion occurs in Battlestar Galactica Reimagined. After  is outed as a Cylon, Adama accuses him of being one of these.   himself however was more of a Poisonous Friend.
 * In season 6 of Supernatural, the Big Bad of the season, to whom both  played Disc One Final Boss, is revealed to be.
 * 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.
 * Subverted in the episode The Great Game from Sherlock. When, we (and Sherlock) assume that he's Moriarty. However, it's soon revealed that.

Miscellaneous

 * 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.

Music

 * Dr. Wily is this to Light, in The Protomen.
 * The music video for "Handlebars" by Flobots.

Tabletop Games

 * In Magic the Gathering, the Big Bad for the Antiquities expansion is Urza's brother Mishra.

Video Games

 * Old school Japanese PC/NES adventure game Portopia Renzoku Satsujin Jiken (The Case of the Portopia Serial Killer) has this as The Reveal, as the titular killer turns out to be The shock factor was so high that nowadays the phrase " is the culprit" is something of a meme amongst old fans. It was even given a Shout-Out in Haruhi-chan.
 * It gets shouted out again in Episode 7 of Umineko no Naku Koro Ni.
 * Flipped around in Dragon Age: 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.
 * from Bully pulled a serious dick move.
 * in  Tales of Symphonia.
 * Once you've beaten the game, one may look back at the story and decide may be another case, but it's sort of hard to tell since he's normally so bloody incomprehensible.
 * And in Dawn Of The New World, without a doubt.
 * We don't actually see the moment of revelation for, but   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 until   finally takes him down.
 * And in Investigations  is shocked to discover that
 * serves as one to.
 * in Castlevania: Lament of Innocence. The series likes this trope: There's also in Order of Ecclesia and  in Curse of Darkness.
 * And in Castlevania Harmony of Dissonance.
 * The possibility is explored in Bomberman 64..
 * 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.
 * in The World Ends With You. as well as a cutscene that starts out short but is slowly revealed (an attempt to confuse the player as to whether  was him or the Reaper, ). Basically, the game switches itself up on you: It intentionally makes you suspect that, then reveals it to be  with some rather convincing evidence, even so far as to make you think that . Then, the end of the game does a 180 and reveals that.
 * Going even further into the "friend" category, it's also been debated that the reason was because . This is evidenced by the fact that, as well as a scene in the manga which depicts.
 * The Boss in Metal Gear Solid 3, 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.
 * The same goes for Naked Snake as Big Boss with the chronologically later Metal Gear as the commander of the young Solid Snake.
 * In Sonic and the Black Knight,
 * 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
 * in Pokémon Black and White.
 * 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,
 * is the Big Bad of Agarest Senki 2. Until  does The Reveal,   was the resident
 * 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...
 * In Fallout New Vegas, Pacer is this to The King. While The King himself is a genuinely good man who does what he can to help out and protect Freeside, Pacer is a xenophobic jerkass who makes outsiders pay a toll in order to see The King (who will at least refund the player personally) and starts fights with the NCR.
 * He is mostly a Poisonous Friend... unless the Courier negotiates a  Then he tries to lead a coup to stop it.
 * In Rosenkreuzstilette, Iris is considered like a kid sister to the rest of RKS, including Tia. Of course,.
 * At the end of Beyond Divinity,
 * from Xenogears isn't only a Big Bad Friend to Fei, he's Fei's.
 * In Paladins Quest, Duke, an apparent classmate of Chezni, is actually Zaygos.
 * In Paladins Quest, Duke, an apparent classmate of Chezni, is actually Zaygos.

Web Comics

 * 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.
 * in Brawl in The Family's "Cocoon Academy" arc.

Western Animation

 * In the South Park episode "The Mystery of the Urinal Deuce", we find out that it was who put the dookie in the urinal. Though it was terrorists who caused 9/11.
 * In several other episodes, 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 keeps pointing this out, though Cartman still seems to think they all believe him.