At first glance, he is the Reasonable Authority Figure or maybe even a Gentleman Detective. However, if you push them too far in just the right place (may or may not be their Berserk Button), he will have a good reason to become an outcast from the police force and perform a FaceHeel Turn. What causes them turn from the law they upheld varies, though disillusionment, disgruntlement or greed will usually be at the root of it.
If the lawman is not the hero of the story, then he might do a full FaceHeel Turn. After helping the hero defeat the villains, he turns on the hero and tries to kill him so he can have the money for himself.
To put it bluntly, this character is what's known as a Lawman Gone Bad. This is a character who takes pride in working for the law before an incident that makes him snap causes him to distance himself from those that he used to work for.
The character may also be a Big Bad Friend.
- This may be the fate of Inspector Finch at the end of V for Vendetta, when the Norsefire system is collapsing. See also under film.
- According to Word of God, this is the backstory of Jackie Boy from Sin City. The audience only sees Jackie as an abusive drunk with an allusion to being a "hero cop" in the past. Apparently, he once earned the accolades of a hero but unknown circumstances led him down a dark path.
- Sheriff Halliday becomes this at the end of Hitman Annual #1, when he tries to take possession of A MacGuffin Full of Money for himself.
- Judge Dredd has several examples, but the most notable is Dredd's own clone brother, Rico. After graduating top of his class, Rico starts taking bribes and running his own rackets while on the job. Joe ends up arresting him and sentencing him to twenty years on Titan, which he actually survives. Rico comes back for revenge and Joe is forced to kill him.
- Former Green Lantern Medphyll, after losing his ring, joined forces with Throneworld's corrupt leader to stop the legitimate ruler from returning and reclaiming his authority. Unfortunately for him, Jack Knight fought back and succeeded in destroying Medphyll.
- A prime example is Captain Culpepper (played by Spencer Tracy) from the 1963 Comedy film It's a Mad, Mad, Mad, Mad World. At first, he intends to confiscate the stolen money and presumably return it to its rightful owners, but after being buried under an ever-increasing mountain of bad news from his home life and regarding his police pension (or lack thereof), he devises A Simple Plan to get the dough for himself and skip on down to Mexico for his "retirement".
- In the western There Was a Crooked Man..., a new warden (Henry Fonda) at an Arizona prison tries to institute reforms, but a Manipulative Bastard inmate (Kirk Douglas) uses this to stage a mass escape. The warden pursues the inmate, and the inmate meets a Karmic Death while retrieving the loot from one of his robberies. The warden returns with the inmate's body and the loot to the prison, but realizes that a new warden has been appointed in the meantime. Disgraced and out of a job, he sends the horse with the body toward the prison while he and the money ride off to start a new life.
- In Minority Report, the trope is subverted. For a while, it seems as if John Anderton will become a murderer, since he's already abusing illegal drugs to cope with the death of his son. In fact, it's his boss, Lamar Burgess, who has been committing murders to validate the pre-crime system.
- Unlike the more ambivalent ending of the Comic Book, the film version of V for Vendetta has Finch clearly joining "V" (actually Evey) when the rebellion against the fascist government begins.
- Ed Kilifer in Licence to Kill. He is a DEA agent who accepts a $2 million dollar bribe to spring drug lord Sanchez from federal custody.
- Harvey Dent / Two-Face from The Dark Knight. Originally the White Knight of Gotham, he goes ballistic and insane after some antics by The Joker. Considering said 'antics' result in, among other consequences, Harvey getting half his face burned off and his Love Interest being killed, this is perhaps a bit understandable.
- In Hard Rain, Randy Quaid's character Sheriff Mike Collig does this. Being forced to stay behind and guard an empty flooded-out town from looters, a town who's citizens just voted you out of office was apparently the straw that broke the camel's back.
- Speed: Howard Payne (Dennis Hopper) was a former member of the Atlanta PD bomb squad, who turned Mad Bomber after being forcibly retired, due to an accident which injured his right hand. He couldn't continue on the force, but wasn't disabled enough to qualify for collecting his pension. Howard did not take it well.
Jack: (over phone) "Why didn't you just come after me?"
- The Czech cop in xXx who, after one too many humiliations, turns informant for the bad guys.
- Max Rockatansky (of Mad Max) started out as a highway cop in a disintegrating dystopian future; he didn't turn bad so much as become a free agent independent of the law in order to go on a Roaring Rampage of Revenge against the motorcycle gang that murdered his family. Then, between the end of the first film and the start of the next one, the apocalypse broke out
- In Rough Cut, Burt Reynolds (The Gentleman Thief) tries to steal a case of rough cut diamonds, being protected by a Police Chief bent on capturing him. After the gang get the case to the Bahamas, Burt reveals that the diamonds are fakes. Cue the entry of the Police Chief with the actual case, "selling" it to them for a share of the cut.
- In The Usual Suspects, Keaton used to be a cop, but since then has been a career criminal for a long time.
- The Alloy of Law has Miles Hundredlives, who was once a good if Knight Templar-ish lawman, but turned to evil when he decided that the political figures he worked for were the real criminals.
- Tomas Sergar from The Children of Man is a secret member of the Brethren, the order of black-aligned mages seeking to take over the world. He is also the head of the Daniyelan Order, this world's international police force.
- Albert Neri in The Godfather.
- Sargent Haig of The Mental State starts out as a Jerkass who looks down on the prisoners he is guarding and regards them as scum. Then, when the prison starts to adopt more liberal policies and the inmates are granted more freedom, he becomes even more sadistic and retaliates by beating one of the frailer prisoners up for no good reason. He gets worse after he is falsely accused of dealing in drugs and incarcerated in the same prison. He even joins up with a criminal gang just so that he can get revenge on the one responsible for framing him.
- Shane is this in The Walking Dead.
- In an episode of CSI, the team investigates a series of killings related to the murder of a mob boss many years before. It's mentioned that a patrol officer called in the car crash/body but mysteriously vanished along with the ill-gotten gains and the possibility of this trope is discussed. It turns out that the corpse that was thought to be the mob boss's was actually his, killed in order to serve as a decoy.
- In CSI: NY, Mac discovers that his first partner became one of these, having stolen a large amount of money from a crime scene (he was nearing retirement and didn't think he was being paid enough) and murdered the girlfriend of the guy who has a vendetta against him and Mac (he doesn't know, then doesn't care that Mac wasn't responsible).
- Inverted in the canceled TV Series Shark where the protagonist, lawyer Sebastian Stark, turns from defending criminals to being a prosecutor.
- In its first and second seasons, White Collar had Agent Fowler, a seemingly corrupt OPR agent who was after Neal, but who turns out to be a case of this: his wife was killed and then he killed her assassin, leaving himself open to blackmail by the Big Bad.
- In "One Way to Get Off", we learn that Gregson's former partner D'Amico planted evidence on Wade Crewes because the police couldn't prove his guilt legitimately. When By-the-Book Cop Gregson calls her out on this, she's more concerned with the potential impact on her career than the miscarriage of justice.
- The villain in "A Giant Gun, Filled With Drugs" is an undercover DEA agent who tries to make some money on the side by kidnapping the daughter of Holmes' old drug dealer.
- The culprit of "Details" is an ex-girlfriend of Detective Bell's, who was also a beat cop. She had been trying to get promoted into Vice, but after learning that Bell went to Internal Affairs with evidence that her late superior was a Dirty Cop on a major drug case they were all working on, her chances were next to nothing, so she took it out on Bell.
- The villain in the It Takes a Thief (1968) episode "The Artist Is for Framing" is a police inspector with a perfect record who's about to retire. He's obsessed with capturing Al as a final triumph, so he commits robberies using Al's techniques and frames him for the crimes.
- Daredevil (2015):
- Benjamin "Dex" Poindexter spends season 3 progressing from an FBI Agent who's overcome some childhood sociopathic tendencies to being Wilson Fisk's most formidable assassin.
- Tammy Hattley, SAC in charge of the FBI protection detail. A seemingly tough but fair boss, who turns out to have spent years being blackmailed by Fisk.
- Ray Nadeem is a downplayed example in that his "going bad" part is because of long-term manipulations by Fisk, and though he tries to fix things, it ultimately proves too late for him and he ends up being killed by Dex.
- Several examples from the Mass Effect series:
- Garrus starts off in Mass Effect as a security officer in the Citadel (as well as a Spectre candidate) but quits due to his Cowboy Cop tendencies and eventually goes vigilante in a Wretched Hive in Mass Effect 2.
- Shepard him-/herself is seen as this by the Alliance and the Council, due to being an ex-Spectre (elite agent of the galactic government) who now collaborates with the pro-human terrorist group Cerberus to deal with alien abductions that the Alliance refuses to acknowledge. In actuality, however, Shepard never goes over to the bad guys, the Illusive Man just did his best to make it look like s/he did.
- Also from Mass Effect 2, the asari spectre Tela Vasir is revealed to have cooperated with the crime lord Shadow Broker after growing disillusioned with proper procedure. She still considers herself serving a greater good, which she believes to justify the questionable means, and calls Shepard out on his/her own cooperation with Cerberus.
- Max Payne
- Max Payne is a NYPD detective in the first two games, but is forced by circumstances (both times involving him being framed for murder of another officer) to go on a one-man crusade against the local mobs both times.
- In a twist for the second game, he actually does kill another detective, except she's a Dirty Cop in bed (literally) with the Big Bad.
- Supplementary material for Max Payne 3 reveals that the Cracha Preto used to be lawmen who went on Vigilante sprees against criminals the law couldn't or wouldn't touch. Then they experienced Motive Decay and descended into being plain paramilitary thugs.
- According to Batman: Arkham Origins, this is the Riddler's backstory in the Batman: Arkham Series: Edward Naston was a member of the GCPD's cybercrimes division before going rogue.
- This Is the Police has Jack Boyt, the protagonist who used to be a competent police chief. Until he's told he has six months until his forced retirement.
- The sequel ramps it up to Lawman Gone Ruthless Badass.
- GoldenEye in Goldeneye Rogue Agent. He apparently went bad after Dr. No shot his real eye out. Then again, it's hinted that he had been a problem for a long time, but this time his luck ran out.
- Numerous examples in Mega Man X, including every single major villain in the first game. The Maverick Hunters are robot police, and one of the most common backstories in the series is 'former Hunter gone rogue.' The reasons vary the most common one is infection by the Maverick Virus, but there are others, especially in the Maverick Hunter X version of the continuity. Sigma, depending on the version, went rogue either because of the virus, to force 'evolution' and draw out the true potential of the reploid race through constant conflict, or both; Sting Chameleon was forced into going rogue because of hostages; Chill Penguin did it out of boredom after having spent so long assigned to Antarctica, Bubble Crab to get rich; and so on.
- Jingles Morgan in the Bravestarr episode "Fallen Idol".
- Christopher Dorner was a textbook real-life example of this trope. His story, told in an 11,000-word manifesto he originally posted to Facebook, was that he grew disillusioned with his job as an officer in the Los Angeles Police Department over the systemic racism and Police Brutality he encountered, and that he was fired for trying to blow the whistle on the use of excessive force. His colleagues dispute his claims, arguing that he was a Loose Cannon who never should've been allowed on the force in the first place. In any event, Dorner was a man who did not respond well to challenges to his personal integrity, leading him to go on a killing spree across southern California in 2013 that saw him kill four people and injure three others (all of them police officers or relatives of such) before dying in an extended siege at a cabin at Big Bear Lake.
- Richard Marinick was a Massachusetts State Police trooper who left the force and joined up with James "Whitey" Bulger's gang. Leonardo DiCaprio's The Departed character is a zigzagged Expy of him.