Poisonous Friend

""We will not allow her to fall from grace. Instead, we will be the sinners.""

- From Afro Samurai: Resurrection

A character defined both by their obsessive loyalty toward a target character and by their vastly divergent (and comparatively "cynical") moral code.

The Poisonous Friend is usually attached to a pacifist protagonist or an idealistic villain. They tend to consider their "master" a person to be worshipped or protected at all costs -- even ones that the master would not knowingly permit.

For example, if the master is a Fettered pacifist completely against killing his enemies, the Poisonous Friend might pay lip-service to this trait while the master is nearby... and then turn around and butcher the enemy behind the master's back. If caught, they'll claim they just "did what had to be done". Few masters catch on.

Sometimes the master's influence gets through to the Poisonous Friend, with results such as Badass Decay. In other cases, the Poisonous Friend continues to pose a danger both to the master's other friends (through jealousy) and to the enemy. The Love Interest is in particular danger of the Poisonous Friend if they suspect them of making the master "vulnerable".

Though sometimes introduced as anti-heroes or turncoats from the other side, they cease to be those things because they place their fundamental loyalty upon the shoulders of their "master". Basically they become a good guy's secretly-evil minion, or a bad guy's much-badder sidekick.

This character is often used when writers don't want to stain the "innocent" master's hands but still need a way to deal with those pesky defeated enemies. Even friends who have been explicitly told to behave or otherwise decided to hold back can still function in this regard if they have done something bad or really bad enough to intimidate the villains. If a particularly noble and idealistic hero has a particularly cruel and ruthless poisonous friend, the villain may hesitate to take advantage of that hero's idealism and kill him out of fear of what his buddy's response could be.

The name of this trope comes from a song by the band Seabound.

If their behaviour actually starts to rub off on the hero, it's Toxic Friend Influence.

Contrast: Psycho Sidekick, Psycho Supporter, The Only One Allowed to Defeat You, Loony Fan, Shoot the Dog. Compare Big Bad Friend. Not to be confused with Poisonous Person, in which someone is literally poisonous, though they can be combined. Also not to be confused with False Friend, in which one deceives another as being their friend, only to have an ulterior motive to do so. A Mysterious Backer might turn out to be one of these.

Anime and Manga

 * Subverted in The Twelve Kingdoms: In the last arc, Kouya initially appears to be a Poisonous Friend to his leader, Atsuyu; he murders dissidents regularly and claims to have "exiled" them when Atsuyu, who is presented in a positively saintly light, asks. However, Atsuyu is revealed to be a Manipulative Bastard who abuses Kouya's extreme loyalty to get away with atrocities while keeping his own hands clean.
 * Death Note: Misa is unwaveringly faithful and supportive of Light Yagami -- and also much cruder and more indiscriminate in her use of the Death Note, which Light considers an insult to his goal of punishing only criminals.
 * Mikami's even worse, killing exactly a page a day, but killing reformed criminals and those that Light thought were redeemable or innocent.
 * Of course, one should keep in mind that over time Light becomes a more indiscriminate killer than either of them, slaughtering anyone that gets in his way, criminal, law enforcer, or innocent.
 * It can be argued that Light's unhighlighted Moral Event Horizon was actually somewhere around the potato-chip incident, where he killed a pickpocket and someone accused of embezzlement and made it crystal clear he didn't actually care about guilt or even crime; the people he was killing were just counters in his game.
 * Code Geass has a pseudo-sibling version of the trope in Rolo, who has an obsessive devotion to his "brother" Lelouch... so much that he wants to prevent Lelouch from reuniting with his real sibling, and even
 * Diethard is another extremist among Lelouch's company. When Suzaku is made Euphemia's Knight, Diethard calls for him to be assassinated. Lelouch suspects that he talked Kallen into trying to kill Suzaku at a party for him at the Ashford Academy, and warns him not to interfere with the military.
 * V. V. is a Poisonous Brother to Charles. He is so devoted to their goal of "a world without lies", . None of this is lost on Charles, who, now fed up with V. V.'s lies,.
 * Fiore from the Sailor Moon R movie is a textbook example; obsessed with his friendship with Mamoru to the point that he'll destroy Earth for his sake, even though that's not at all what Mamoru wants.
 * Yubel from Yu-Gi-Oh! GX, one of Judai's Duel Monsters, who he apparently sent into outer space when she started killing anyone who defeated or upset him. She now holds a homicidal grudge against Johan because of his friendship with Judai.
 * The Chessmaster Kyoya Ohtori (and, to a degree, all other male members of the Ouran High School Host Club) is utterly devoted to the idealistic and naive club founder Tamaki Suou, and is not above using dirty tricks and even threats to cover up for his blunders from the shadows, which Tamaki generally fails to notice. This is most evident in episode 14 ("Covering the Famous Host Club").
 * An especially absurd example would be Legato from Trigun, who decides to torture and kill Vash while Knives, the Big Bad, is recovering from his last encounter with Vash, knowing that Knives will kill him when he wakes up.
 * Also Wolfwood in the anime, most notably when he shoots Zazie the Beast, who looked like he might have been calming down.
 * Manga Wolfwood too, kinda. Their philosophical division gets even more development here, and Vash is a darker character though he doesn't kill anyone, but despite Wolfwood's huge conflicts over what's "right" (which ranges from putting a bullet in the back of Vash's head for the good of humanity to actually considering Vash's position) he's mostly of the opinion that you have to make sacrifices if you're going to save anyone. Hanging around with him is a catastrophe waiting to happen for Vash, although Vash doesn't help. And he survives and makes spaghetti for the guy who did it. This series is whacked.
 * Manga Wolfwood shoots Rai-Dei the Blade in a situation analogous to the Zazie one mentioned above. (Anime Wolfwood shoots Rai-Dei offhandedly in the ruins of August with no witnesses, probably on Legato's orders, and shooting manga Zazie is kind of...irrelevant, since the collective can always find a new host.) He and Vash have a major blow-out about it, but after Wolfwood manages to top the drama-meter by holding Vash's gun to his own forehead and demanding that he pull the trigger and walk forward, able to kill his own enemies and survive, because dying would be worth that, they keep traveling together.
 * It's not like Vash didn't have some idea what Wolfwood was before, but the protect-shooting can't be ignored like stuff he hasn't actually seen, so it's a crisis point in both media. Manga Wolfwood is much stronger in his defense of his position because the anime adaption was Lighter and Fluffier even once it got serious, and Vash's philosophy got considerably more positive reinforcement, despite keeping him as Iron Woobie.
 * Wolfwood's also defining his place as Poisonous Friend in the gun moment, because Vash is condemning him for killing Rai-Dei, so it's saying both 'get rid of me, then, if you don't want what I'm willing to do for you' and 'without me, you'll have to do your own killing, do you really think you can handle that?'
 * The fact that Wolfwood is also, simultaneously, The Mole, The Lancer, and the best friend Vash has ever had seriously complicates the issue.
 * Yuno from Mirai Nikki is Yukiteru's creepy stalker-for-a-girlfriend. She'll gladly risk her own life to protect Yuki, and she won't think twice about slaughtering anyone who dares to harm him. She's also extremely jealous, and Yuki finds himself struggling to convince her not to kill his friends.
 * Johan of Monster served as Anna Liebert's Poisonous Brother, murdering anyone their pursuers might have possibly used to pinpoint their location, before she finally caught on and
 * He also helps Tenma's promotional woes. By killing off all his superiors that were keeping him down. And depending on your interpretation,
 * Even if that wasn't his central goal, he certainly wanted to do that.
 * Alucard of the Hellsing Organization clearly qualifies as Sir Integra's anti-conscience by the way he is able to stir Sir Integra into giving him the most ruthless orders so he can indulge his bloodlust as well as succeed in whatever mission he is sent to.
 * It's semi-subverted as he implies that she enjoys it, though. Which she does not deny, only saying that it's 'none of your business'.
 * It's debatable as to weather or not she enjoys it, as her telling him to shut up about it may be because she wants to cleanse that from her mind.
 * Also, if you insult, harm, or threaten his master, you'd better have someone to save you, otherwise you will regret it.
 * Shizuru of Mai-HiME could be seen as being one of these to Natsuki; the latter seems pretty horrified when she sees that Shizuru has in the name of 'protecting her'.
 * Maki from Seto no Hanayome.
 * Paul von Oberstein plays this to Reinhard in Legend of Galactic Heroes,  and later.
 * Walter von Schenkopp occasionally plays this role for Yang Wenli, often suggesting that Yang should consider seizing power for himself, forming his own nation, or . This is mostly because Schenkopp honestly feels Yang would do better than the pack of Ungrateful Bastards they've been working for who have alternately . One of the prime differences between Reinhard and Yang is that Reinhard listens to Oberstein, while Yang usually rejects Schenkopp's suggestions due to his moral code and general lack of ambition.
 * Black Cat: Creed Diskenth takes this to creepy extremes. He has such a constant hard-on for Train that at one point he ruthlessly butchers three intelligence officers for referring to Train as 'that guy'. The kicker is that he does this just after Train, once a heartless assassin, reforms and abandons the life of a killer, deciding to never take another life. Train pays little attention to the fact that Creed goes on a killing spree anytime Train's honour is insulted. (Note that Train's refusal to kill is exclusively in the anime, not the manga, nor does Creed perform acts of killing based on percieved slights to Train in the manga)
 * Gilbert from Pandora Hearts is utterly dedicated to his master Oz and will do anything to protect him. Although he hasn't yet killed anyone (onscreen, anyway) for Oz's safety and well-being, he's tried, without any hesitation - despite being the gentlest, sweetest, most pathetic character of the series. However, his backstory flashbacks show that he cold-bloodedly allowed himself to be adopted by an 'enemy house' to become nobility and to steal their secret family weapon (the Chain called Raven), and then became an assassin, all in order to gain the power to save Oz.
 * Oz himself has had a scary unnatural breakdown in which he wanted to do this for Alice, to stop her from suffering.
 * Hunter X Hunter:  has recently become this to  . After  .   is determined to kill.
 * His Heel Face Turn, mind, in no way involved making nice with the heroes. It probably didn't even involve not conquering the world. It just involved attempting to discuss terms with Netero like civilized beings. Which, all things considered, was a pretty huge breakthrough.
 * Especially since the last time it looked like he was having a moral crisis (because of Komugi) he turned out to be leading up to triumphant laughter over how much more marvelously powerful it meant he was, that he could kill and eat any human despite our newly recognized tremendous variety of potential.
 * Too bad Netero was determined to stick with the blowing up plan. On the other hand, Meryem is the scariest thing ever, so I can understand the desire to try to wipe him out with no caveats.
 * The Wolkenritter in Magical Girl Lyrical Nanoha A's could count. They go out to complete the Book of Darkness despite Hayate ordering them not to, which would seem to make them an example, but they do it regretfully and only because they believe it's the only way of saving her (which is not far from the truth). They go so far as to avoid killing people so that Hayate won't be responsible for murder.
 * Perhaps Reinforce could also count as she, after seeing that, targets those she thinks are responsible: . Hayate makes it very clear that this is not what she wants.
 * Kino's Journey: Kino meets a woman traveling with the intent of spreading peace, but the man she is traveling with is a highly skilled gunman. He kills people trying to attack the woman and she is none the wiser.
 * Conrad Weller in Kyou Kara Maou quite frankly states that he is this to Yuuri in relation to both Greta and Hube, who respectively tried to kill Yuuri to please her racist guardians and to get Conrad to kill him, and who Yuuri wants to save and protect when they're disabled afterward. Conrad's first priority will always be Yuuri's safety, no matter how cruel he has to act.
 * This is carried to its logical conclusion in the Daishimaron arc, when
 * The God in the spoiler above
 * In Naruto  is revealed to be one to his Rival,  . In an effort to keep the village safe, and prevent the idealistic   from having to tarnish his image , a Black Ops organisation that has been involved in all sorts of unpleasant business over the years, all, at least in his mind, for the good of the village.
 * In Durarara:  is revealed to be this to   How bad is   willing to protect   Well
 * Also
 * A lot of other Durarara characters follow this pattern too. Mikado, Kida, and Anri are all willing to be this for the naive, nice people they believe the others to be. Walker and Erika are this for Kadota, though he has some idea about what they're doing while he averts his eyes.
 * Homura in Puella Magi Madoka Magica, to Madoka. She threatens to kill, attempts to kill , and in fact does kill.
 * Worth noting, though, that in her case.
 * Homura in Puella Magi Madoka Magica, to Madoka. She threatens to kill, attempts to kill , and in fact does kill.
 * Worth noting, though, that in her case.

Comic Books

 * Johnny the Homicidal Maniac: NNY meets a fan who idolizes and copycats his work because he thinks it's just that cool. NNY is outraged because he doesn't kill for the fun of it -- he does it because he needs the outlet to survive his role as a "Flusher" for the world's negativity. (NNY then proceeds to do to the copycat what he does to everyone.)
 * Also, oddly enough, this becomes an example of Even Evil Has Standards as well. It is implied by NNY's killing rant that the impostor raped a woman, and that NNY would "never do...that". (Though, this may be more because NNY loathes physical contact than anything else.)
 * Depending on who is writing, Batman is this to the entire Justice League, and the superhero community at large. Hard not to be when your team mates stumble across detailed plans on how to kill each and every one of them in case they go rogue and have to be put down.
 * Professor Xavier had similar plans at one point. Of course, given the number of times a hero's gotten Brainwashed or hypnotised or had some other Enemy Exchange Program weirdness happen to them, that probably isn't such a bad idea. Of course, the fact that he included one for taking himself down probably mitigated any hard feelings.
 * DC Comics' controversial Identity Crisis storyline turned a small group of lesser Justice League members into this for the League at large. While the Big Three heroes like Superman, Batman, and Wonder Woman went about living and acting on their ideals, lesser members would do necessary "clean-up" jobs to preserve the League's secrets, primarily by having Zatanna wipe minds and even reprogram someone's personality. Used as a Retcon to explain away events where the villains learned (or should have learned) the identities of various heroes, but never acted on them.
 * DC Hero team, The Outsiders. The Outsiders have had three different incarnations over the years. They were founded by Batman, whose ties to the League had become strained. He has stated his intent to use the team as a black ops version of the Justice League, able to take the proverbial "fall" in public opinion where the League cannot.
 * One of the interpretations of Captain America's sidekick Bucky was as the guy who did the backstabbing Cap was too moral to do.
 * Another is that Cap wasn't too moral for that kind of work, but that his public image could not be so sullied. There are several instances where Cap is portrayed as accepting, even approving, of Bucky's "extracurricular activities," although there are quite a few where he is not.

Fan Fiction

 * Takashi in the Deva Series is one to Hayate, using underhanded means to protect her interests, including.

Film
"Operative: I believe in something greater than myself. A better world. A world without sin. Malcolm: So me and mine gotta lay down and die so you can live in your better world? Operative: I'm not going to live there. There's No Place for Me There... any more than there is for you. Malcolm, I'm a monster. What I do is evil. I have no illusions about it but it must be done."
 * The Operative in Serenity fills this role for the controlling central government. He himself observes that the purpose of his actions is to maintain an ordered society for people unlike him. In the end

"I'll bring us through this. As always. I'll carry you, kicking and screaming, and in the end you'll thank me."
 * Tyler Durden very much fits this trope in Fight Club.


 * Nicky Santoro in Casino is the source of all of Sam "Ace" Rothstein's problems. Rothstein went from a powerful, rich, and successful casino manager and lost it all due to the attention the mobster Nicky kept drawing to him. Note that Casino is actually based on a true story though names were changed for the film.
 * Sean Penn's character (a lawyer turned gangster) was the poisonous friend to Al Pacino (a former gangster trying to go straight) in Carlito's Way.
 * Mean Streets: Johnny Boy is this to Charlie.
 * In MST3Ked film The Brute Man The Creeper is willing to kill to take care of the blind pianist Helen.

Literature

 * Dolores Umbridge in Harry Potter and the Order of the Phoenix knows that Cornelius Fudge would never permit her to, but as she says, "What Cornelius doesn't know won't hurt him." Hell, even the book synopsis on the dust cover describes Umbridge as having "a personality like poisoned honey."
 * Or maybe it just becomes "what Cornelius doesn't know can't be linked to him by the press and force him to resign".
 * Not to mention the secret of Dumbledore's childhood:
 * In a more complex way, and probably not intentionally, it's Snape for Dumbledore, being the Bad Teacher for Harry (Dumbledore obviously being the good one). His constant nitpicking, bickering and sneers served to harden Harry's spirit and helped him not to get a swelled head. Not that it was pleasant.
 * The Biblical figure of Joab in Second Samuel. As King David's general he frequently performs David's dirty work including orchestrating the death of Uriah the Hittite (on David's orders) so David may marry Uriah's widow, Bathsheba, and executing David's son Absalom for rebellion, against David's orders. While Absalom's death enables David to remain king, David publicly mourns for Absalom, and eventually orders Joab to be killed.
 * Even then, David didn't technically give the order. Solomon gave the order on his behalf, after yet another betrayal and David confiding in him about Joab's past actions.
 * For another poisonous friend in the Bible, try Jezebel. She led Ahab to worship false gods, and had the prophets of the God of Israel killed, as well as those who worshiped the true God. After several years of perversions, lies and murder, things eventually came to a head. Her husband (and the King of Israel), Ahab, wanted the vineyard of Naboth. Naboth refused to sell, despite good offers of money and better land elsewhere. Jezebel had Naboth killed on trumped-up charges of blasphemy against God and the King, thanks to two false witnesses she paid off.
 * God sent Elijah to talk to Ahab, as he went to take Naboth's field. Elijah cursed Ahab and Jezebel as enemies of God: both were eventually killed, Ahab in battle, and Jezebel by being tossed out of the window.
 * In Patrick O’Brian’s Aubrey-Maturin novels, the dual protagonists are frequently each other’s poisonous friend: each man has been known to aid his dearest friend’s missions by conducting hostilities in ways that are appalling to the latter’s sensibilities or morality--the swashbuckling captain Jack Aubrey with large-scale naval carnage, the surgeon/intelligence agent Stephen Maturin with cold-blooded assassination and deception.
 * Maturin also reads other peoples' mail. Aubrey is not cool with that.
 * And, on the flip side, while Aubrey is by no means a "flogging captain" he uses the lash sometimes, much to Maturin's displeasure.
 * The novel Shady Corners by Mathew Williams has a Poisonous Friend as the protagonist. It's every bit as creepy a read as you'd expect.
 * Suzette, Lady Whitehall. Wife of the straightforward and honest Raj Whitehall, he survives the Byzantine machinations of the Governor's court despite his total lack of aptitude for such things... because Suzette is entirely happy to seduce and manipulate his rivals, poison his enemies, and arrange for obstructionist officials to be quietly dropped into the river with a sixty-kilo roundshot chained to their ankles. All without telling him, of course. Disturbing because he is WELL AWARE of what she is doing and yet is on occasion preachy about the morality of doing it.
 * The whole purpose of Contact's Special Circumstances division.
 * Rare protagonist example: Harry Dresden to Michael Carpenter, his good friend, who is a (literal) Knight in Shining Armor and has an uncompromisable code. So, in Death Masks, he asks Michael to leave the room while he breaks the legs of Quintus Cassius.
 * And then Ebenezar is something of a Papa Wolf Poisonous Friend to Harry.
 * Harry didn't appear to have any problem with
 * Lasciel acts like a poisonous friend to her hosts in order to corrupt them.
 * Perrin's loving girlfriend and wife Faile in The Wheel of Time. Besides being a very jealous type and giving him a hard time over any woman she suspects might want him, she also indulges in all the dirty aspects of politics he considers to be wrong, including sabotage, espionage, manipulation and assassination. Some of those things he tells her not to do, but she doesn't listen. The rest, he just doesn't know about...
 * That's doubtful, as he knew the type of woman he married, especially after meeting her parents. It's more of a contrived ignorance, as he is very aware of just how ruthless she can be. It's more that he knows better than to ask as he would probably not like the answer.
 * The Gentleman with the Thistledown Hair in Jonathan Strange and Mr. Norrell gets it into his head that working as a butler constitutes abuse for Stephen Black, and decides that because he's handsome and courteous, he needs to be king of something. He even tries to get him to kill the king of England for this reason, and Stephen has to explain that it doesn't work like that.
 * There's a dark sort of Overly Long Gag late in the book where The Gentleman tells Stephen a rambling story of the lengths he went through to find Stephen's "true" name and the many people he ended up murdering directly or indirectly in the process.
 * Vimes and Vetinari in Discworld. Unusual in that the Poisonous Friend is actually the protagonist's boss.
 * Lord Montfallcon does this for a living in Gloriana by Michael Moorcock, working behind the scenes to maintain order because he fears his queen's idealistic policies aren't enough to secure the realm's new golden age.
 * Valentinian in Belisarius Series has some aspects of this; not only is he Belisarius' bodyguard, he is his personal executioner and hatchet man. When Belisarius wants some shocking bit of violence done he simply says "Valentinian..." which is shorthand for Off with His Head.
 * Monk Mayfair is just short of this to Doc Savage. Philip Jose Farmer theorizes that in addition to Savage needing someone who can kill (not to mention lie, steal and seduce), Mayfair's obvious enjoyment of these gives Savage vicarious pleasure.
 * The Knight and Rogue Series has a mild example in Fisk. While Michael is so righteous that he won't even tell a white lie, and encourages Fisk to follow this example, Fisk is willing to lie like hell or con his way out of a situation when need be-usually when Michael isn't looking. He becomes less of one by the third book, though.
 * The Corrupt Corporate Executive Cassandra Cautery is all kinds of this to Dr. Charles Neumann in Max Barry's Machine Man. She claims to have his best interests at heart, but is clearly only looking out for Better Future.
 * Stephen King's thriller Thinner gives us an anti-heroic example: Protagonist Billy Halleck is cursed to die by a pack of traveling Gypsies after accidentally killing the leader's daughter. Billy's best friend, mafioso Richie Ginelli, responds by poisoning their guard dogs, shooting up their camp (without killing anyone), and assaulting the clan leader's granddaughter. The old leader takes the curse off, but Ginelli is killed by said granddaughter in the end.
 * From the novel Surender, Finnegan is this to Gabriel.

Live Action TV
"Frasier: What kind of a woman are you? You seduced me, you lied to me, you nearly got me killed. You've shamelessly manipulated not only me but the station, the news media, and the entire city of Seattle. What do you have to say for yourself? Bebe: Aren't you glad I'm on your side?"
 * Bebe on Frasier was a classic example of this: the completely unscrupulous agent. Frasier was frequently warned that agreeing to anything she suggested, however favourable and seemingly innocent, was tantamount to dealing with Satan.

"The Doctor: Oh, and this is my friend River. Nice hair, clever, has her own gun. Oh, and unlike me, she really doesn't mind shooting people. I shouldn't like that. Kinda do, a bit. River: Thank you, Sweetie."
 * Saul Tigh on the 2000s Battlestar Galactica earns this title a bit literally. He's best friend to Commander/Admiral Bill Adama (Galactica's resident beloved leader). He's usually the guy rooting for a good fight rather than diplomacy, and occasionally, is right in doing so. But he's a liability. Time after time after frackin' time, Adama goes out on a limb for Tigh - hiding the truth of his alcoholism, appointing him XO even though he's "not cut out for command", and whitewashing, then forgiving, most of Tigh's screwups (including shooting civilians aboard the Gideon, a military dictatorship, the use of suicide bombers on New Caprica, and showing up drunk to testify at Baltar's trial). Though he occasionally has to Shoot the Dog to keep the blood off Adama's hands (see the entire New Caprica arc and the S3 episode "Hero"), one shudders to think how far  will go in the service of Bill Adama.
 * In an odd case, Tigh himself has his wife Ellen, who encourages his alcoholism and tries to get him to be more assertive and ambitious. And betrays resistance plans to the Cylons to keep him alive..
 * He is this way up until . It is very likely his destructive behavior and drinking were his way, but YMMV...
 * In Star Trek, "Section 31" performs questionable actions in (preemptive) defense of the Federation. Played with a bit, as when they first surfaced in Deep Space Nine the Federation was actively trying to shut them down; Enterprise sort-of retconned them into originally being the black-ops wing of Starfleet Intelligence, and apparently losing their budget and official status at some point seems not to have slowed them down much.
 * cites this trope as his reason for secretly betraying Captain Janeway in an early episode of Star Trek: Voyager, saying that his role requires making the morally dubious choices she can't make in order to get the crew home. She doesn't take it well.
 * Doctor Who:
 * Leela from has no qualms about violently disposing of anything or anyone that threatens the Doctor, despite his many attempts to rein her in.
 * Captain Jack Harkness is willing to go quite far to protect the Doctor, using methods that the Doctor would never approve of.
 * River Song takes this trope Up to Eleven, willing to  just to keep the Doctor alive. It frustrates him terribly. On the the other hand, he does admit that her methods are useful at times:

"Dalek: Records indicate you will show mercy. You are an associate of the Doctor. River: I'm River Song. Check your records again."
 * Neatly summarized when River faces a Dalek:

"Angel: "Were you even listening?""
 * Buffy the Vampire Slayer: Giles on several occasions, in particular beating the crap out of Ethan in "Halloween", killing Ben in "The Gift", and plotting with Robin to kill Spike in "Lies My Parents Told Me". And  in the Season Eight comics.
 * He even gives a nice speech about it in "The Gift".
 * Really, all of the cast for both shows are this for all the others (besides for Dawn, Tara and Lorne). We've seen them all without the others (Wishverse Buffy, Dark Willow, Ripper, Angel after firing everyone and a few others) and they're all much, much worse without the others. So it's like Conservation of Ninjitsu, only with evil.
 * In a subversion, when Fred plans to murder (Or at least trap inter-dimensionally, which probably a death sentence) her old college professor, who did the same to her and at least four other people, her boyfriend Gunn kills him for her, in an attempt to pull this off. Fred does not take this well at all.
 * This, of course, was on Angel. Another example would be Wesley shooting Knox in cold blood right after Angel gives a speech to him about being merciful to their enemies.


 * On Charmed, Cole kills a corrupt landlord who is trying to blackmail Phoebe. This is a turning point in one of his several backslidings into evil.
 * Burn Notice plays with this trope. Michael is hardly a boy scout himself, but it's implied in several episodes that hanging out with a Handsome Lech FBI informant and Ax Crazy arms dealer and former IRA terrorist are not exactly helping his standing with the intelligence community.
 * Conversely, Sam and Fi are portrayed as good influences compared to some of the people Michael has had to get into bed with in the course of investigating the people who burned him. A particularly strong example is Larry, Michael's former mentor-turned-Psycho for Hire Career Killer, who's always showing up trying to convince Michael to join him. In a sort of inversion, Larry thinks that Michael's true potential is being stifled by his association with his present comrades.
 * The Good Wife includes Fred Weller guest starring as a Jerkass Amoral Attorney. It's implied he acts this way in part because he believes his boss deserves someone watching his back and willing to get their hands dirty. Good thing, too, because it was the only thing giving his character depth.
 * On Luther, the eponymous Scotland Yard detective has Alice Morgan, a former Child Prodigy who brutally murdered her parents and got away with it, and has now developed a crush on the copper who investigated the case. Luther really doesn't appreciate her attempts to help him get back together with his estranged wife, which seems to involve a lot of breaking and entering and assault.
 * Walter White is this to Jesse Pinkman in Breaking Bad. While Jesse wasn't completely innocent before getting into business with Walt, it's undeniable that his life has taken a definite turn for the worse because of Walt's influence. Of note is the fact that Jesse is equally as poisonous to Walt, but unintentionally, and in a completely different way: while his sincerity might be debatable, we continue to see Walt goes to impressive lows in order to ensure Jesse's safety, despite the fact that he is an emotionally volatile wild card and a liability. Add this to the fact that Jesse is the one who gets Walt into the drug business in the first place, and you have a recipe for one of the most mutually poisonous friendships on television.
 * Community Jeff's friends Alan. Even after Jeff helps him become a partner in the firm, Alan still won't admit that he was the one that got Jeff disbarred.
 * Revenge has Nolan, who's actually an inversion of sorts: while he assists Emily Thorne in her titular revenge gladly and is significantly more cynical than she is, he also frequently points out she could easily just go off to enjoy her life and leave the people who wronged her behind.
 * The Criminal Minds episode "The Performer"
 * In an interesting Sitcom variant, Lily from How I Met Your Mother is revealed to be this, breaking up Ted's girlfriends if she thinks that it will be better for Ted (and, by extension, herself).

Theater

 * In Othello, Iago convinces Othello that Desdemona is cheating on him, leading Othello to end up killing her...and himself.

Video Games

 * Lampshaded, doubly-subverted, Deconstructed, and mixed in with a little Psycho Supporter in Brink. The Resistance has some rather extreme followers who are willing to do anything if they think it will help Brother Chen and the Resistance. At one point, one of them says that they will do the dirty work while Brother Chen, the much more reasonable leader of the Resistance, will be able to keep his hands clean. The Subversion comes when Chen mostly tolerates such soldiers, since he sees them as necessary for the war effort and for his political promotion. Its Deconstructed through Moekena, who looks at Chen and the radical followers and sees a vile leader who uses others so that he doesn't get his hands dirty instead of seeing a conflicted leader who has to deal with dangerously extreme but necessary followers, since Moekena does not know of Chen's point of view. Its doubly subverted when
 * Princess Sapphire has some interesting ideas on how she should help Almaz once she learns of his predicament. Most of them involve killing someone, as almost all of her ideas do.
 * Soren in Fire Emblem: Path of Radiance toes the line of this, acting as Ike's second in command and advisor and constantly discouraging sentimental decisions. He goes over Ike sometimes to make sure his friend stays safe, but doesn't take this trope to its fullest extent.
 * It becomes obvious that Ike is the only person Soren cares about, but in Radiant Dawn, he's somewhat more willing to go along with the decisions Ike makes.
 * Alexa in Command & Conquer 3: Kane's Wrath.
 * Axel to Roxas in Kingdom Hearts. He seems like a pretty cool guy, but a single playthrough of Chain of Memories is more than enough to see how wickedly treacherous he can be, and he shows it off more towards the end of 358/2 Days. Obsessed with keeping Roxas and Xion as his friends, he lies to them, does questionable stuff behind their backs, and if they try to leave the Organization of their own free will, he attempts to bring them back by force. Though, Roxas does wise up near the end and replies in kind by leaving. Axel
 * It's not just the desire to keep them as his friends. He knows that going against the Organization means death, and that meeting with Sora will end In short, he's (at least in part) trying to protect his friends by lying to them, forcefully keeping them in the relative "safety" of the Organization, and generally making a bad situation worse.
 * And then he tries to kill Roxas.
 * Rider is Sakura's poisonous friend in HF route Fate/stay night. She's willing to let the world be destroyed or kill Sakura's love interest and sister just to prolong her life an extra couple days if she has to, whether Sakura wants her to or not. And Archer probably counts as Tohsaka's, though his loyalty is rather ambiguous most of the route and definitely takes a second place to his real goal.
 * She gets a bit better later on in the route, as she realises that Sakura just being alive isn't sufficient, and even ends up fighting against her. She's still acting almost exclusively for Sakura's benefit, though.
 * Even Saber does this for Shirou, to a limited extent. She has just as many objections to killing innocent people as he does, but she has absolutely no qualms about killing enemy masters, even defeated ones (like Ilya), and is far more interested in winning the war.
 * In Persona 4, this is what Shadow Chie says about Chie towards Yukiko. She states that since everyone else likes Yukiko better for being prettier, Chie feels a certain need for controlling her. While Chie ultimately is forced to admit that there's truth in this, the player can help her develop into someone who wishes to protect others for the sake of protecting.
 * in Tales of Symphonia, whose
 * Sodia from Tales of Vesperia.
 * In World of Warcraft, Makuru is one to Obadei, insisting on taking vengeance against the orcs after learning that they killed Obadei's brother.
 * In Dragon Age, Morrigan kind of fits this since she approves of the Warden's more ruthless actions and dislikes his/her more compassionate ones. A better example appears on the antagonists' side: Arl Howe to Teryn Loghain. Arl Howe does seem genuinely loyal to Loghain and his political and military support is a great boon to him as well. However, he is such a Complete Monster that Loghain supporting him and making him Arl of Denerim will help to screw him over in the Landsmeet if you bring up some of Howe's actions
 * Kreia in The Sith Lords qualifies. She has an obsessive and controlling attitude toward your character, vehemently opposing the addition of most of your party members and even any associations with NPCs who seem to threaten her hold on you. One major difference is that, rather than try to keep you pure, the lessons she imparts to you as your mentor are usually geared toward you becoming a Manipulative Bastard: in conversation, a sociopathic response is usually the way to make her happy. Bonus points if you choose The Dark Side, as most of your party members who care enough about you to try to intervene attribute it to Kreia's bad influence on you.
 * Kreia doesn't really approve the sociopathic option-which tends to be Stupid Evil or Chaotic Stupid-so much as she approves of whatever option benefits you and the party most; whether it's considered right or wrong is not the issue. Ruthless, cunning, and self-reliance ) she encourages, not pointless cruelties. In her mind, keeping you on a more middle path is keeping you 'pure', and uncorrupted by the teachings of the Jedi and the Sith. She's... interesting like that.
 * Depending on how moral you want to play it, Steven Heck is this to Mike in Alpha Protocol, murdering and framing innocents to help his buddy.
 * In Disgaea 4: A Promise Unforgotten, Fenrich vowed to make the vampire tyrant Valvatorez the greatest in all the Netherworld. The only problem? Somewhere along the line, Val seems to have developed some sort of pesky conscience, has sworn off human blood (which has massively De Powered him), and has insisted on following a new code of evil which is not very evil at all. Fenrich has no intention of giving up his original vow, so...
 * Some of Fenrich's ideas tend to cross a few moral lines (but never THAT one, thankfully). During Chapter 5, he goads Valvatorez into promising him that he will take down Vulcanus should she pose an obstacle to their plans... and then goading her into a fight with them by blowing their bounty out of proportion. Right in front of Valvatorez!
 * In the first God of War, Ares honestly seems to think he did Kratos a favor when he tricked him into murdering his own family. During their final battle, Ares basically throws a fit and claims that Kratos had no right to turn against Ares after everything Ares did to make him stronger. At the end when Kratos has Ares at his mercy, Ares makes one last plea for his life by telling Kratos that he just wanted to make Kratos a great warrior. Unfortunately for Ares, he succeeded.
 * Commander Shepard from Mass Effect is accused of being one, albeit unintentionally, by Admiral Rael'Zorah in 2 due to Shepard's return for the dead causing his daughter, Tali, to nearly immediately file a transfer request to join them on what is essentially a suicide mission.
 * Matriarch Aethyta also gets in on this in 3, noting that Shepard's influence has lead to Liara dealing with some severely sketchy people in the last 3 years. Considering Liara spent the past 50 years beforehand as an archaeologist working alone on dig-sites, which Liara herself noted have less explosions, Aethyta definitely has a point.

Webcomics

 * Richard from Looking for Group is an extreme example. He started as an evil character who found Cale'anon (one of an unspecified "evil race" committed to truth and justice) entertaining, but found himself gradually swept up in the cause, acting as one of Cale's lieutenants. He cemented himself in this role when he was brought before a demonic court to answer for all the good he's done in aiding Cale'anon.
 * Pella would be a better example, as she commits a crime to further the main character's cause.
 * The trial was specifically about a particular village that he slaughtered; though he thought he was doing evil at the time, demon scryers found that had he not done so, they would have eventually become an invasion force that would subjugate the entire continent. The net moral worth of his act was therefore deemed "good" and he was, essentially, on trial for neglectful virtue.
 * Pee Jee and Aubrey fit this trope for Davan of Something Positive. Hurt Davan in any way and they will respond with tenfold the pain you caused him. Davan is not always bothered by this.
 * In Men in Hats, Aram attacks Sam with a steamroller in the name of putting Gamal's plans into action, and Gamal is pretty sure steamrolling people wasn't his idea. (Aram has also been known to literally poison his friends.)
 * In El Goonish Shive, Nioi acts on the assumption that Lord Tedd would be better off without his personal Blood Knight. In turn, General Shade Tail's opinion of Nioi is pretty low.
 * Anakin becomes this for Palpatine in Darths and Droids.

Western Animation

 * Beezy J. Heinous on Jimmy Two-Shoes. In His Friend Versus Lover rivalry with Heloise over Jimmy, he can get just as Yandere as she can (see: "Best Bud Battle"). He has also stolen money from Jimmy at one point.

Real Life

 * Perhaps a real-world example would be an aide to President Theodore Roosevelt, who was said to have shot the famous bear spared by the president.
 * Somewhat understandable at second glance, seeing how Roosevelt had already bagged its mother without realizing she had a cub, and leaving an orphaned juvenile bear to fend for itself would have been far more cruel than simply shooting it.
 * He did what had to be done. Sometimes that actually IS the good road...
 * In another presidential example, some claim that most of Barack Obama's cabinet are of this ilk, basically getting down and dirty in debates and issues so he doesn't have to come off as a jerk. Particularly true of Rahm Emanuel, notorious for being Obama's hardass attack dog (even following a Congressman into the shower to help secure his vote). If an American version of The Thick of It were to be made, the Trans Atlantic Equivalent of Malcolm Tucker would probably take heavily after him (it helps that Emanuel even kinda-sorta looks like Peter Capaldi). Of course, Emanuel is now Mayor of Chicago, so said adaptation would have to be a bit unrealistic...
 * Gaius Scribonius Curio, and to an extent Marcus Antonius, were poisonous friends to Gaius Julius Caesar during the political conflicts leading to the civil war and during the civil war. They would often give a far more aggressive image of Caesar and his motives, probably in their part contributing to the eruption of the civil war. At one occasion Curio told someone who wasn't decided on who to join in the war that Caesar's thus far merciful and gentle attitude toward conquered (Roman) enemies and encountered neutrals was just for the moment and soon his (Caesar's) cruel nature would emerge from the facade. This was completely contrary to what Caesar liked to present himself being like, writing to Cicero that, "Nothing is more alien to my nature than cruelty." (Gauls would disagree.) In the times leading to the civil war, Curio would insinuate that Caesar was ready to start a war if his requirements (a consulship following directly after his proconsulship in Gaul) weren't met. This, of course, only added fuel to the flame for his enemies, who saw that as long as it was Caesar who would start the war, they'd gladly join the fight and no doubt win. In fact, a lot of Caesar's political allies had a very similar mindset, and neither Caesar nor Pompey actually wanted to go to war, though they were absolutely prepared for it.
 * Some real life lawyers for benevolent or naive celebrities are perfectly willing to knowingly be assholes if it means protecting their deserving employer. A rare positive example.