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.
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.
Hive is one of the original Inhumans, a random prehistoric hunter kidnapped and personally modified by the Kree in horrific experiments to turn it into the leader of their armies. Thousands of years later, it gets a chance to fight one of those same Kree, and is clearly enjoying it despite its stoic nature.
Hive: I'm not that frightened hunter any more.
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.
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).
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.
The Mexican skit series Chespirito featured an hourlong segment starring "Los Caquitos." In that episode, El Botija, the self proclaimed leader of the "gang" orders his partner, El Chómpiras, to steal a large sum of money from a pawnshop. When Botija divides the money, Chómpiras gets one bill starp, La Chimoltrufia, Botija's wife, gets two bill straps, and Botija gets three bill straps. Chómpiras protests this division since he did all the work, but Botija justifies this by saying he's the boss and Chimoltrufia is his second in command. That night, Chómpiras sneaks into Botija's apartment, steals the money and gives back every cent to the pawnshop.
In the Cold Case episode "Knuckle Up," the killer's son (who had himself accidentally killed someone) does this to his dad.
Arthur Lennox: If you do this... you're going down.
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," after the Doctor decides to Take a Third Option to prevent Gallifrey (and the Time War) from escaping the Time Lock, Rassilon attempts to kill him. Cue the Master saving the Doctor by blasting Rassilon with lightning and taking vengeance on him and the Council for using him as a beacon since he was 8 years old via the drums in his head (and thus causing his insanity.)
In one episode of Forensic Files, a group of youths (including the victim's ex-girlfriend and best friend) teamed up and killed their tormentor after dealing with his years of abuse. Here's a small list of what he did
Raped his ex-girlfriend
Had his best friend attacked by a dog
Made derogatory comments about his best friend's girlfriend's weight
Picked fights with people at the gym
Got an elderly man who was attracted to him to do a gay porn then showed it to his friends, then when the man refused to do a sequel, beat him up.
Lancel Lannister to King Robert Baratheon. 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 in "The Children" after the latter condemned him to death for a regicide he did not commit, which was simply the latest and greatest slight Tywin committed against his son, after treating him like dirt for almost his entire life. Despite Tywin's efforts to try and gain control over the situation, he gets crossbowed while on the privy. Tyrion also kills Shae (his lover) for betraying him at his trial, before fleeing Westeros.
In the same episode, his sister Cersei also finally gets back at her father. Tywin refuses to budge from shipping her off to an arranged marriage so Cersei plays her trump card: she threatens to destroy House Lannister by telling everyone the truth (the incest between her and her twin brother Jaime which has been going on for years). Tywin seems confused about what "The truth" is, and at first Cersei scoffs that he is merely feigning ignorance. With growing realization, she assesses that even the brilliant Tywin Lannister never noticed what was going on between his own children, when all it would have taken was one attentive moment in the past twenty years. Tywin is still apparently confused, so with a merciless grin Cersei reveals that all of the rumors about her and Jaime (and the children he thought were her ex-husbands being Jaime's) are true – she will tell everyone and destroy Tywin's vaunted family legacy, even though it will also mean her death and her son Tommen's death.
An almost literal example from Sansa Stark in Season 6. After Jon Snow gives a No-Holds-Barred Beatdown to Ramsay Bolton and decides to leave the bastard at his sister's mercy, Sansa savors every second of telling abusive husband Ramsay that House Bolton dies with him, before siccing his hounds which he had starved for a week on him (making this a literal example), walking away with a Psychotic Smirk on her face as he screams in agony.
Daenerys, when she finally stands up to Viserys.
Daenerys: I am a Khaleesi of the Dothraki. I am the wife of the great Khal and I carry his son inside me. The next time you raise a hand to me, it will be the last time you have hands!
One of Craster's wives stabs Karl Tanner during his duel with Jon Snow.
A literal example when Ghost kills Rast during the Night's Watch's assault on the mutineers, who had spent the previous episode reveling in tormenting him while he was caged.
The knights and nobles Tyrion antagonized (rightly or wrongly) over his time at court line up to testify against him by restating his words and threats verbatim (although out-of-context) in "The Laws of Gods and Men".
Nymeria literally does this to Joffrey on Arya's behalf when he's bullying her.
It's been implied that Jaime's murder of Aerys was a case of this. In the books, this is confirmed, since among other things Jaime was forced to stand by and listen as Aerys brutally raped his wife Rhaella and whilst Brandon and Rickard Stark were horrifically killed, and Jaime would "go inside" his own mind when that happened, implying that it left him with a degree of PTSD.
Kevan refuses to meet Cersei as soon as he returns to the Capital. In the books, Cersei wasn't allowed to meet anyone until they got a forced confession from her. But Qyburn comes and meets her before so apparently she does have visitation rights.
Tyrion has been treated like crap ever since the Battle of the Blackwater, as he was maimed in an assassination ordered by his nephew, rejected by his father, unappreciated for his efforts and forced into a betrothal he didn't want. So when Joffrey tries to organize a bedding for him and Sansa with a rape-y undertone, Tyrion publicly threatens to geld him with a steak knife which leads to a Stunned Silence.
The Unsullied were raised like animals by the Wise Masters, who mercilessly tortured them into hardened killing machines. Dany's first order lets the Unsullied show their Wise Masters just how good they are at killing.
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.
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."
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...
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 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.
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 lollipop after he tried to make his head explode and allowing a gangster to beat Forrester up, mistaking the doc for Frank.
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.
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.
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.
A major point in the 2016 remake ofRoots is that, as the producers stated, they didn't want to show Kunta and his family as just passively suffering through slavery, but that Kunta retained his pride and never gave up fighting back against his enslavers. The odds are against him and he cannot fight every white man in Virginia, but the remake makes it a point to show Kunta and other slaves managing to actually kill at least a few overseers - keeping people enslaved who don't want to be is a constant, dangerous business. Unlike in the original, Kunta later directly gets revenge on the brutal overseer who whipped his back to shreds by choking him with his own gun, leaning into his face and shouting "My name is Kunta Kinte!" while watching the life drain out of the overseer's eyes.
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.
Bridgit Pike turns against her brothers after they misteat her and sets them on fire.
Tabitha Galavan has enough of the rather crappy way her brother Theo has treated her and his niece, Silver St. Cloud, when he tried to kill the latter. She proceeds to knock him out, give his parachute to Silver, and escape with Silver as Gordon arrests Theo.
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.
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...
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.
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.
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.