Cheers. Frasier in "The Heart Is a Lonely Snipe-Hunter". It was his Establishing Character Moment, and he didn't do it because he was mean or angry - he accepted being a victim of a snipe hunt because that's what guys do - and screwing the others would also be what guys do. At that moment, Frasier earned some Hidden Depths.
In the Doctor Who episode "Last of the Time Lords", after the Doctor has talked down Francine Jones from killing the Master, the Master's wife shoots him after being driven insane by his abuse. She gets another chance to kill him (or at least try) during "End of Time, Part One" when she actually sacrifices her life to try and disrupt a resurrection ritual for him.
In "End of Time, Part Two," the Master decides to trap himself, Rassilon and the rest of the Time Lords in the Time War for them implanting the sound of drums in his head.
Played with in the third season finale of Boardwalk Empire; Gyp Rosetti is (literally) stabbed in the back by The Dragon Tonino, but even though Rosetti has given Tonino ample cause to bite back all season, Tonino's only doing it because Nucky and Eli forced him to (although in one final Kick the Dog for Rosetti, the only reason Tonino was in a position to be threatened was because Rosetti left him behind when the shit hit the fan).
In Kamen Rider Ryuki, Scissors (known in America as Incisor) has a slightly different ending than the one in Dragon Knight: when a Rider's Transformation Trinket is broken, the contract with his Contract Monster (Advent Beast) is broken as well... and the second Volcancer is free of Scissors, he promptly eats him.
In 24, Jacob Rossler, terrorist engineer, keeps Inessa Kovalesky, a fifteen-year-old Russian girl, as a sex slave; when found, she is clearly in shock, has been severely abused, and wants nothing more than to go home. When told that she has to go with Rossler (the U.S. government required Rossler's help to deal with a greater terrorist threat, and he demanded full immunity along with being allowed to bring Inessa with him), Inessa smuggles a pistol into her jacket and kills Rossler at first chance.
In a flashback on LOST, Eko and two henchmen are about to fly a plane full of heroin out of Nigeria. Eko's brother and the military show up, everything goes awry, and the surviving henchman takes the opportunity to push Eko out of the plane and fly off with the heroin by himself. Of course, he crashes on the island and dies.
In season 3, Ben held Jack captive with the intention of having him perform spinal surgery on Ben. Ben sent Juliet to convince Jack to do it, and she brought along a VHS of what she said was To Kill a Mockingbird. But the video ended up being of Juliet holding cue cards telling Jack that Ben is dangerous, should not be trusted, and that Jack should kill him on the operating table. Viewers were originally led to believe that she was attempting a Klingon Promotion, but she had completely different reasons for wanting him dead...
Subverted in Pretty Guardian Sailor Moon: when Jadeite came to Beryl when their base was being destroyed, and requested her to exit, Beryl said that she's tired of being a fake queen, and ordered Jadeite to leave, but he wouldn't leave her. So Beryl removed the brainwashing from him, and was surprised to see that even with free will, he chose to stay with her.
Attempted in the fourth season of The Wire, wherein Rawls reveals Burrell's manipulation of the stats to the newly elected Carcetti. Backfires when Carcetti lacks sufficient political clout to have Burrell fired.
In the second season premiere of Stargate Universe, Dannic, one of the Lucian Alliance soldiers, takes over for Kiva and establishes his character immediately by choking one of his subordinates when she doesn't give the answer he wants. Later on, as he becomes irrational and refuses to surrender, she shoots him in the back.
On Weeds, U-Turn was killed when he suffered a heart-attack while trying hiking. Instead of getting help, his remarkably fat lieutenant just smothered him as he lay on the ground. A few too many fat jokes pushed the guy over the edge when he saw his chance for revenge and a Klingon Promotion.
In the episode "And They Are Us" from Airwolf, the leader of the badguy's mercenary force does this in a couple of ways, including knocking out the badguy so the heroes can escape.
At the beginning of season 4 of Babylon 5, Lyta Alexander is treated as a slave by the second Vorlon ambassador. She is the one who lures him into an ambush.
In one episode of The Muppet Show, Beaker, Butt Monkey assistant of Dr. Bunsun Honeydew, gets put in a duplicator. The army of Beakers, once assembled, proceed to chase and harrass Bunsun throughout the episode, eventually supplanting the rest of the cast by the end, even Statler and Waldorf.
Lancel Lannister to King Robert Baratheon in Game of Thrones. He got Robert excessively drunk while on a boar hunt and his inebriation led to him getting mortally wounded by a boar.
Tyrion finally bites back against his father Tywin after the latter condemned him to death for a regicide he did not commit, which was simply the latest and greatest sleight Tywin committed against his son. Despite Tywin's efforts to try and gain control over the situation, he gets crossbowed while on the privvy.
Once Upon a Time: Jefferson (The Mad Hatter), tired of being kicked by Regina (The Evil Queen) every time he helps her, bites back by freeing (amnesiac) Belle from her prison and telling her to find Gold (Rumplestiltskin, who in this universe is also the beast) and tell him that Regina locked her up. Jefferson himself doesn't have it in him to kill Regina himself, but he knows for a fact that Gold does, especially once he finds out that Reginalied to him about Belle's death.
Snow, after having been screwed over by Regina and her mother Cora one time too many, including the murder of both her parents as well as the maid who was a mother figure to her after the fact, finally retaliates and curses Cora's heart and then tricks Regina into putting it back into her mother's body, killing her.
Partially subverted in that people constantly assume that Merlin is a weak stepping stone and can't do anything about their abuse of him, but he's actually an insanely powerful sorcerer with very little problem killing anyone in his way. Protip: Calling him "nothing but a serving boy" generally means you're going to die.
In the Tales from the Darkside episode "Baker's Dozen", the evil witch who makes voodoo dolls out of cookies regularly torments her assistant by turning him into a mouse. The assistant vows to get even but the witch mocks his anger. Near the end, she turns him into a mouse yet again after they had made another batch of a dozen cursed cookies. She realizes too late that her assistant had made a baker's dozen (thirteen) cookies, with the thirteenth cookie representing her. She screams in agony as her mousey assistant nibbles on the cookie...
In Person of Interest Kara captures Snow and uses him to run errands for her, using the constant threat of a bomb-vest to keep him in line. She takes great pleasure in commenting on how well she's managed to break him at one point. When she doesn't need him any longer she locks him in a room and sets the vest on a timer... only he manages to get out and is waiting in the backseat of her car when it detonates, killing both of them.
In Primeval, Oliver Leek is torn apart by an army of predators he created.
A literal example in an episode of Taxi, Alex rescues a dog from his abusive owner. The owner eventually comes back with the police claiming Alex stole his dog. After listening to both sides, the cops decide to let the dog choose who he wants to go with. Much to everyone's surprise, the dog runs towards his old owner. None of the cabbies can figure out why until they see the dog bite his owner on the hand.
More than a few of the murder victims in various Law & Order episodes are this, but an especially noticeable one was in the SVU episode "Bully." An employee of a high priced wine company had secretly been recording her Bad Boss screaming and hitting her. The employee was eventually murdered, but not before setting up a timed e-mail to leak the videos to various media outlets, exposing the boss for the bitch she was, ruining the business, and driving the boss to suicide. As he sees the videos on the news, Elliot says, "Well, well, well, the church mouse finally roared."
Mystery Science Theater 3000 had TV's Frank turn against Dr. Forrester a few times, though the Doc bit even harder. Notable moments including smashing Forrester in the head with a giant lolipop after he tried to make his head explode and allowing a gangster to beat Forrester up, mistaking the doc for Frank.
Agents of S.H.I.E.L.D.: When Mike Peterson/Deathlok gets free from Garrett's control in the first season finale, he immediately turns on him, killing him in retaliation for ruining Mike's life and turning him into a monster.
On Salem George Sibley had Issac whipped and branded him as a fornicator. Years later he begs Issac to help him. This trope is lampshaded by both of them, and encouraged by John Alden. While torn over it, Issac ultimately tells Increase Mather when he suspects that something happened, and Sibley is rescued.