In the Season 7 episode of Curb Your Enthusiasm titled "The Black Swan," Larry tells Marty that introductions are a pointless and unnecessary social convention. Later, when Marty didn't introduce the Stonemason as Larry was calling him an asshole, Marty reminded him of his own policy regarding introductions. Larry responds "So I'm hoisted on my petard."
Larry David is late for a dinner because he's behind someone who takes a long time at a doctor's appointment, so he tells the doctor that patients should be admitted according to their appointment time. Later, he races to sign in at the doctor ahead of someone, but ends up going behind her because of the new policy, which goes with what David had ordered.
In the Stargate Atlantis episode "The Tower", the villain dies due to a scratch from his own poisoned dagger. It is likely that this is a deliberate reference to the above-mentioned work of William Shakespeare, where Claudius and Laertes are both done in by the very poison they had conspired to kill Hamlet with. (Well, Claudius also gets stabbed a little bit. And, in one notable adaptation, hit by a chandelier.)
The Huntsman from The 10th Kingdom. Earlier in the miniseries, we are told that his magic weapon is a crossbow that, when fired, shoots bolts that will not stop until they hit the heart of a living being. So quite naturally, during the climax when he and Wolf are struggling over the weapon and it is accidentally fired upwards through the skylight, the rule of Karmic Death (as well as the law of gravity) dictates the arrow comes right back down and stabs the Huntsman in the heart from behind.
In Primeval, Oliver Leek amasses a mind-controlled army of vicious predators from the future in a bid to obtain power. This royally screws up when the mind-control device breaks, and the predators kill him.
Similarly, the woman who had raised a sabre-toothed tiger from a cub that she found is killed by it at the end.
In the Grand Finale of Star Trek: Voyager, the Borg Queen is tricked into assimilating Future-Janeway, causing her to contract a nanovirus (ten years in the making and about seventeen ahead of its time), killing her... again.
In the earlier two-parter "Year of Hell", the Big Bad uses a ship that has the power to Ret Gone anything. Janeway's Heroic Sacrifice causes the ship to target itself and everything that happened in the episode is undone. Oddly enough, this actually gives the Big Bad a happy ending — he had unwittingly wiped out his own homeworld and family when he used the ship during a war. With the ship gone from the timeline, the life he lost had been restored. Though he is once again working on temporal calculations.
In the Star Trek: Deep Space Nine episode "Civil Defence", the crew accidentally triggers an automated defense program left behind by the station's previous commander, Gul Dukat. After the crew's failure to circumvent the program triggers the station's self destruct, Dukat himself shows up and offers to save them if they give his people massive diplomatic concessions. He then attempts to beam off the station to let the crew mull his offer over, only to discover that one of his superior officers installed a similar program in case he ever tried to leave the station after triggering the self-destruct, an act that the superior officer considered to be Dukat abandoning his post. The program prevents Dukat from leaving the station and prevents him from using his access codes to stop the self destruct.
The villain wasn't killed in the Doctor Who episode "Dalek", but Henry van Staten surely paved the way for his eventual fate. His policy of using torture on his alien captive caused said alien to go on a murdering rampage when it finally got loose, and his fondness for wiping people's memories and dropping them off in a town starting with the same letter as their last name got turned around on him by his newly appointed second-in-command.
Goddard: And by tonight, Henry Van Statten will be a homeless, brainless junkie living on the streets of San Diego, Seattle, Sacramento... Someplace beginning with S.
In Genesis of the Daleks, when the Daleks turn on Davros and his followers Davros (in his one and only moment of compassion) begs the Daleks to have pity on the scientists who helped to create them - but they don't, because Davros did not include pity in their data banks. More or less the same exact thing happens every single time he appears- he makes more Daleks to replace the batch the Doctor has killed, and they turn on and either kill or imprison him soon afterwards. You'd think he'd notice the pattern at some point, but no.
Similarly, in "The Age of Steel", John Lumic is defeated because all devices in the parallel universe are capable of interfacing with each other, allowing Mickey and the Doctor to get the code to deactivate the emotional inhibitors into the system.
Lumic's own creations also turn on him at one point:
In The Robots of Death, Taren Capel is killed by his own robot revolutionaries when Leela uses helium to change his voice.
Not forgetting "Evolution of the Daleks", where The Cult of Skaro's human soldiers, when contaminated with Timelord DNA, end up destroying the Cult's own Dalek Thay and Dalek Jast.
And "Last of the Time Lords" when the Archangel network The Master used to become Prime Minister allows humanity to pool its psychic energy to restore The Doctor.
The Second Doctor actually uses this phrase in The War Games after subjecting the scientist to his own processing machine.
Alright everyone, pop quiz! The Earth is secretly ruled by a species capable of both editing people's memories and giving them post-hypnotic suggestion and have controlled mankind for over 10,000 years. How do you defeat them? Answer: Use the suggestion the aliens arrogantly supplied you to have them tell mankind to kill them all on sight.
And how do you make sure everyone has received the suggestion? Embed it as static in one of the most watched videos of all time. The Moon landing right between "one small step for man" and "one giant leap for mankind". You could be killing them right now and not know it.
The Time Lords created a method for saving themselves from the Time War by implanting a signal in the Master, which drove him insane. No surprise he eventually causes the undoing of their plan by turning on them and helping the Doctor save everything else from the Time Lords' plan.
Then there's the Plasmavore from "Smith and Jones", who had been hiding from Judoon scanners by feeding on humans and incorporating their DNA. Then the Doctor lets her feed on him, and as we (especially those Judoon scanners) all know, he's not human, either.
The Carrionites in The Shakespeare Code are defeated by William Shakespeare using the source of their power, language, as a weapon against them.
When the Cybermen decided to make Craig Owens their Cyberleader, as the process started he heard his baby cry and through sheer willpower broke free, but the Cybermen already connected to him felt his pain and emotion which caused them to overload and explode.
A variation in "Asylum of the Daleks", where the Dalek's nigh-unbreakable network (connecting every single Dalek to each other) is hacked by Oswin Oswald (who is having trouble accepting being converted into a Dalek herself and pretends she's just shipwrecked) to forget anything about the Doctor, as a few of their rejects try to kill him. When the Doctor then returns to their mothership, they have no idea who he is.
Interestingly, Daleks are not machines but blobs of flesh integrated into saltshaker-like forms, meaning Oswin hacked living beings.
Serially averted by The Master throughout Season Eight. He repeatedly tries to destroy life on Earth by unleashing an alien menace, only to end up helping the Doctor defeat it after realising in the nick of time that it's as much a threat to him as anyone else.
In the LOST Season 4 finale, Ben kills Keamy with Keamy's own knife. It also works on a metaphorical level; killing Keamy has the result of killing everyone on the freighter, including innocent people; Ben had been avoiding killing innocents until Keamy "changed the rules" by killing Alex. Thus Keamy dies by his own weapon and as a result of his own actions.
On an episode of Law & Order: Special Victims Unit, a killer was captured in Canada, with the defense arguing that he shouldn't be extradited, because he could be executed for the murder upon return to the US. (The Canadian government is politically opposed to the death penalty.) When the judge asks if that wouldn't result in Canada becoming a haven for American killers, the attorney says that's only a theoretical possibility and shouldn't influence the decision. Then ADA Alex Cabot announces they only want to extradite the perpetrator for kidnapping and car theft, which aren't capital crimes. When the defense complains that it's just a ploy so they can get him back to the US and then charge him with murder, the judge (with obvious amusement) points out that it's just a theoretical possibility which won't necessarily influence his decision. Owned!
Example of did not do the research because 1) Article 12 of the US-Canada Extradition treaty specifically forbids this manuever and 2) the state of New York has not executed anyone since 1963.
In the original Law & Order, the police suspected a Japanese tourist of traveling to America to have his wife killed for the insurance money so he could pay off the Japanese mob. But by the time they figured that out, the man had already gone back to Japan. While the Japanese man was "mourning his wife," he badmouthed America for having so much violence, and when first questioned by the detectives, said a black man did it. The DA's office was having trouble extraditing the man, so DA Arthur Branch puts out a fake story that they had captured the shooter and needed the Japanese man to come back to America and identify him. The man does return, and is promptly arrested. Branch even cited this trope as his plan.
In another episode, McCoy tries to use the fact that former ADA Jamie Ross called in an anonymous tip to exonerate one of her clients on death row to force her to plea bargain in another case. Rather than do that, she resigns as her client's counsel, tells him to keep his mouth shut, and reports herself to the State Bar. Adam Schiff shakes his head ruefully and tells McCoy "By your own petard, m'boy."
On Law & Order: UK, DS Brooks confronts his corrupt ex-partner who has been trying to implicate him in the theft of evidence. After taking the box of cigarettes that Brooks offers him, the Genre Savvy man frisks him and finds that he's wearing a wire. After destroying it, he confesses to having had someone else steal the evidence. At this point, the doubly Genre Savvy Brooks reveals that there's another microphone hidden in the pack of cigarettes. If only he'd curbed that nicotine addiction...
In an early episode of Law & Order: Criminal Intent, the villain is a professional mob hitman known for taking great efforts to cover his tracks, such as (in the show) putting a victim in his deep freeze (a la real-life example Richard "The Iceman" Kuklinski) to slow down the post mortem process and thus make the victim's time of death appear later than it was. After he appears to have completely gotten off, Detective Goren drops a hint that there is possibly some remaining evidence in his garage, whereupon he spends a night tearing up the floor looking for it ... something he would only do if he had consciousness of guilt. The detectives arrest him, in his garage, in the morning.
In the Pie-lette of Pushing Daisies Chuck laments that she was hoisted by her own petard - her vacation was also smuggling monkey figurines, which got her killed. It prompts Ned's reply, "What's a petard?"
Colonel Flagg fell victim to this in his final (and no-doubt most humiliating) scheme on M*A*S*H When Hawkeye put the welfare of a communist soldier over another patient since the communist was in worse shape then the other patient, this naturally led to Flagg thinking Hawkeye was a Communist Sympathizer. Flagg made the mistake of recruiting Major Winchester into spying on Hawkeye; but he sorely misjudged Winchester's character. Winchester duped Flagg into thinking that a camp bridge game (which included the mayor of Uijongbu and his brother, the city's chief of police, as guest players), was a meeting of conspirators, which Flagg then attempted to raid. Even though they found out that Major Winchester set the whole thing up, the two angry South Korean officials vowed to use their US military contacts to ensure that Flagg would be punished; and since Flagg was never seen again in this series, they apparently succeeded.
In Life (season 1, "Powerless"), the main villain becomes obsessed with Reese (they both go to the same AA meetings, and he figures that she lied about her dark past), so he holds her hostage in her kitchen and forces her to drink a massive bottle of vodka, and finally she tells him about her past in a totally awesome speech, and when he looks away for a second, she grabs the empty bottle of vodka and whacks him across the head with it, thus giving her partner and his backup time to break in and save her.
In The Closer episode "Tijuana Brass", a corrupt Mexican cop looking for an accused murderer (who plans to testify against the drug cartel the cop works for) has the word spread among locked up convicts that whoever kills the guy he's looking for will get a big reward. After his corruption is ultimately revealed and the protagonists arrest him, his former coworkers book him under the name of the guy he had put the hit on, which results in him being murdered in prison.
Nonfatal example: the humourless forum administrator in the children's television program Lift Off was in the habit of digging up new things to ban, at one point producing a ban sign with a mirror on it. Then he was convinced to turn it around. Then pure force of Lawful Neutral kicks in.
One episode of CSI: Crime Scene Investigation featured a woman and her father who co-owned a construction company and wanted to end the marriage to the woman's husband without getting a divorce, since Nevada divorce law would give the husband half of her shares in the company. They try to frame him for attempted murder, since Nevada law also requires that criminals not profit from their misdeeds, which would have meant the husband wouldn't get anything belonging to his wife. The scheme backfires horrifically when the CSIs uncover the woman and her father's plan and charge them with conspiracy, and it's implied that, under the very same law they tried to use to deprive the husband of any part of the construction company, he's going to end up owning the whole thing.
Meanwhile, in Miami, a wife uses the fact that she's part of a set of triplets to set up what seems to be an airtight alibi for herself (and thus, all of them) for her husband's murder. Except it turns out that the husband has been using a body double because of his high profile job, and the body double was the one who died.
In one episode of the new Battlestar Galactica, in Season 2, a big Cylon Raider fleet fleet is disabled by a Cylon Logic Bomb, which they previously planted onto Galactica.
The inventor of Hymie the KAOS robot on Get Smart gets killed by his own invention. Something similar happens to many Big Bads, including "Mr. Big" in the pilot.
The inventor of the Cybernauts on The Avengers gets killed by his own invention, as does his brother who tries to follow in his footsteps.
Invoked in Robin Hood...sort of. Guy of Gisborne gives his sister Isabella a vial of poison, intending for her to use it. She instead laces the blade of a dagger with it and stabs him in the back. On the other hand, Guy is also impaled on the sheriff's sword, an injury which kills him before the poison gets a chance.
The Sheriff of Nottingham is blown up by explosives that he himself brought into the castle.
On Merlin, Hengist, villain of Lancelot and Guinevere, is killed and eaten by the pet monster he'd spent the whole episode feeding people too.
By the end of season three King Uther discovers that his genocide against magical users has turned his own illegitimate daughter against him.
Morgana succeeds in her plan to make Guinevere look as though she was cheating on Arthur with Lancelot and have her banished from Camelot - unfortunately, these actions put Guinevere in a position where she is able to overhear Morgana's plans to invade Camelot, and race back to sound the alarm.
On Supernatural, this happens all the time, normally to the humans who mess with the dark arts. They always get what's coming to them, and almost never from the main characters.
Plus this is what the Trickster does to his victims. Ironically, it's also how he dies. He tries to trick Lucifer by creating a doppelganger of himself, but since Lucifer taught him how to do that in the first place, he easily sees through it and kills the real one.
And in the Season 4 finale, Ruby reveals herself as The Mole and is killed by the Winchesters with the same demon-killing knife she's been carrying around for the last two seasons.
In the Sanctuary episode "Sleepers", Tesla loses his powers by his own "Devamper", which was powered by the very ability it ended up taking away. And really his own fault for making both ends of the weapon functional.
On Spike TV's One Thousand Ways To Die, a pair of dimwitted terrorists were blown up by their own bomb when they forgot about daylight savings time while setting the device's GPS-based timer.
The Big Bad of Dollhouse, Boyd Langton, spent a good portion of S2 manipulating the main cast into creating and handing over a device capable of wiping and imprinting anyone, not just Actives. Topher uses it to wipe Boyd, reducing him to a Doll-state, and he blindly—happily!—follows Echo's instructions to strap a bomb to his body and blow up the Rossum headquarters.
In an episode of The Adventures of Superboy, a demon turns Loretta York into Yellow Peri, a powerful witch who wreaks havoc. When Superboy confronts them, Yellow Peri sets a photo of him on fire. Like a voodoo doll, this causes him to burst into flames, falling to the floor and screaming in agony. The demon laughs and mocks him. Angrily, Superboy blasts him with heat vision, but it has no effect. The demon smugly boasts that only magic can hurt him, and Superboy immediately grabs him, causing the fire to spread to him and reduce him to ashes. Fortunately, with him gone, his curses wear off, Superboy is healed, and Yellow Peri reverts to Lorretta York.
Non-death example: In the sixth-season episode "Older and Far Away," Dawn makes a wish to the vengeance demon Halfrek that everybody would spend more time with her. Halfrek makes the dream come true by magically making it impossible for any of the guests at Buffy's birthday party to leave the house. She then comes and taunts them... until she realizes that she can't escape the house, either, and reluctantly reverses the spell.
In Yes, Prime Minister, Sir Humphrey enacts a masterful gambit to ensure that the Employment Secretary is removed from his post after suggesting a brilliant idea to move large sections of the armed forces Oop North, which has received much hostility from senior civil servants and military officials because they'll, well, be Oop North and far away from Harrods and Wimbledon and all the nice cushy things down south which they like. He expertly plays on Hacker's paranoia to make Hacker think that the Employment Secretary is using this plan as part of a coup to secure Hacker's job. It works, the plan is scuttled, the Employment Secretary gone, and Humphrey is left to leave in smug satisfaction of another job well done... until in the last minute of the episode, Hacker realizes that now the Employment Secretary is gone, there's nothing to stop him safely implementing the plan...
Models Inc. ended with Emma Samms' character getting shot by a hitman she'd hired to shoot her ex's new wife-to-be at the wedding... but most viewers never saw this, as the original broadcast of the episode ended on a Cliff Hanger at the fatal gunshot. Aaron Spelling had the foresight to film an alternate ending in case of cancellation note but not enough foresight to also bring closure to Carrie Anne-Moss' storyline; if anything, Emma's death would have made things even worse for Carrie.
In Medium episode "You Give Me Fever", the guy responsible for causing another guy to kill himself after infecting him with a deadly contagious disease. The villain took a vaccine to protect himself. Allison confronted him but there was no proof other than her visions. The woman was upset until she had another dream. The villain was allergic to the vaccine so he had to take steroids to counter the reaction but it made him vulnerable to the flu. He was last seen in the hospital dying.
In the final episode of Blackadder II, Ludwig the Indestructible prides himself on being a Master of Disguise, and plans to use this, and the knowledge that Nursie always goes to fancy dress parties as a cow, to infiltrate Queen Elizabeth's court. Unfortunately, his pride in his disguises means he makes the mistake of disguising himself as a cow, rather than as a mad old woman with an udder fixation.
In Psych's first season, episode twelve ("Cloudy With A Chance of Murder") features Shawn and Gus as legal consultants to the defense of what seems to be a hopeless case. There's a mountain of evidence against them, and just when they're starting to get an advantage, the prosecution produces a video that provides proof of the defendant's guilt. With Shawn's hyper-observative skills, he uses it to instead prove her innocence and force the real perpetrator to confess.
An episode of Cold Case featured a villain who would abduct women and imprison them in a windowless cell for months in order to break their spirit. Once this was achieved, he would leave them there to starve to death. However, he stashes his latest victim within hearing distance of a church that rings its bells every Sunday. With this, the woman is able to keep track of the days and retain her sanity. Her refusal to snap rattles him so much that he finally makes a mistake that gets him arrested. To top it off, at the episode's end, we see him being tossed into a cell very much like the one he'd barricaded his victims in — and he's claustrophobic.
In another episode, the villain, who had been correctly identified as the prime suspect when the case was still hot, framed someone else for the murder and went to the police himself to get the case reopened, in the hopes of getting the other guy arrested and himself cleared. Needless to say, his doing this backfired.
Still another had a particularly loathsome killer forcing his little niece to watch the murder to "teach her a lesson." Guess whose testimony turns out to be just the evidence the cops need to put him away?
Frequently the premise of Tales from the Crypt episodes. For example, one episode had an adulterous woman killing her wealthy soap magnate husband when she realized he'd gotten wind of the affair and that she would get nothing in the divorce. She takes his body to the soap factory and dumps it into the compressor, then takes the bars of soap home, intending to wash them down the drain, but then getting the macabre idea to take a shower with them. Suddenly she begins screaming in pain and we see that her skin is rapidly developing disfiguring welts and blisters, being destroyed by the gastric acids that are now present in the "soaps". The show ends with her wailing in agony, huddled on the floor of the shower, the water turning red with her blood.
The trope name is said in full on at least one occasion in series 2 of Robot Wars. The robot in question, Caliban, had a flail weapon to run the gauntlet with. When Sir Killalot came along, it picked Caliban up by the flail, prompting Jonathan Pearce to say the phrase. As Caliban ended up last with a measly 0.2m, it makes the trope very literal.
In the Bones episode "The Bullet in the Braincase", a sniper who has been using the names of other snipers in order to purchase supplies (and sticking them with the bills) is located when Booth discovers a piece of land bought using his name. When Booth confronts him, the sniper taunts him to jump the fence and enter the property without a warrant. Booth jumps the fence and points out he doesn't need a warrant; after all, the property belongs to Seeley Booth. Cue the Oh Crap look and the suspect running away.
One episode of Hogan's Heroes had Hogan explicitly invoke this trope to describe how a plan had gone wrong/would go wrong.
The Villain Protagonist of "The Bellero Shield" is Judith Bellero, the scheming wife of an idealistic scientist, who learns the hard way that Ambition Is Evil as she's subjected to this trope twice. When a gentle alien who protects himself with an impenetrable force field is accidentally drawn to her husband's lab, Judith kills him and passes off the force field as her husband's invention. Judith demonstrates the force field on herself—but realizes too late that only the alien can turn it off! Although the alien turns out to be Not Quite Dead and frees her before expiring, her guilt over the murder drives her insane, a la Lady Macbeth, and at the end she imagines herself still trapped behind the shield. "Nothing will ever remove it..."
In "The Special One", alien invader Mr. Zeno poses as a human teacher to indoctrinate child prodigies. It turns out that the kid he's currently working with was playing Fake Defector all along, and uses one of Zeno's own weapons to force him to retreat to his home planet.
In "Checkmate," Number Six determines which of his fellow villagers are prisoners and which are guards by observing their mannerisms (prisoners are meek and submissive, while guards are defiant and confident). Using this knowledge, he recruits a team of prisoners to make an escape...and is foiled when they notice how confident and defiant he is, become convinced that he is a guard testing their loyalty, and turn him in to Number Two.
In "A Change of Mind," the new Number Two uses psychological tactics cribbed from the Red Scare and the Cultural Revolution to turn the whole Village against Number Six, declaring him an "unmutual" and ostracizing him. At the end of the episode, Number Six, pretending to have been converted by the experience, persuades Number Two to call the whole Village together for his public confession and repudiation of his sins. Instead, he uses the opportunity to declare that Number Two is "unmutual." The villagers, conditioned by Number Two to automatically believe such accusations, form an angry mob and run him out of town.
In "Hammer Into Anvil", Number 6 uses Mind Games (and the inherent paranoia of the Village) to drive the current Number 2 into reporting himself to the authorities for incompetence.
In the episode with Hamlet, Mike challenges Pearl to a Shell Game, winner gets to choose the movie. Mike wins and decides on Hamlet and mentions "any version". Boy, does Pearl give him Hamlet!
In the Series Finale featuring Danger: Diabolik, Pearl goes on a madcap spree, pouring Mountain Dew on Brain Guy's brain, then futzing with the Satellite of Love with a remote control. When the controller breaks and engages the reentry protocol, she can't fix it because Brain Guy's brain is still messed up!
Season 9's episode featuring Werewolf had Mike attempt an escape from the Satellite of Love. When Crow and Tom realize that he's not coming to get them, they move the ladder over Castle Forrester.
In Mighty Morphin' Power Rangers season two, Lord Zedd and Goldar's chased the Rangers to a far-off planet with the powerful superweapon Serpentera. Impatient, Zedd decides to use Serpentera's main cannon to create an Earth-Shattering Kaboom despite Goldar's pleas. The Rangers escape with what they were looking for as the planet is destroyed and Zedd chases the Rangers back to Earth. When he tries this again, Serpentera's batteries run out of power, forcing him to retreat!
Used a few incarnations later in Power Rangers Lightspeed Rescue, but this time it's the good guys on the receiving end. The Lightspeed Aquabase was built underwater in order to ensure that the demons would be unable to reach it. However, when the Season Finale arrives, one of the Elite Mooks uses a magic card that he stuck on the leg of their strongest Megazord to allow their Mooks to swarm the base and destroy it. And their main weapons were the rangers' own zords, which they hi-jacked.
Slightly subverted in the series finale of the Original Ultra Seven. When the finale monster Reconstructed Pandon catches Ultra Seven's Eye Slugger and tries to kill him with it, Ultra Seven turns it around on him and kills the monster like he originally intended.
"Where and When": A murderer using Cinderella's knife to turn victims to glass ends up getting stabbed with it, leaving behind a beautiful glass corpse.
The first season finale of Strike Back features the Big Bad, Latif, attempting to use VX gas on the leaders of several European countries and the United States by implanting explosive canisters filled with the nerve agent inside a pair of suicide bombers, while simultaneously kidnapping Grant and a Pakistani presidential candidate, all to expose the truth about Pakistan's invovlement in a plot to plant WMDs in Iraq to justify the war. Little does he know that Grant had grabbed an empty container (the explosive core of which is volatile enough to be set off by a direct hit from a bullet) recovered from his Chechen base in the previous episode. So when he tries to force Grant into a car at gunpoint, she points the gun at the canister (still on her, somehow) and pulls the trigger for him.
Daniel Hardman of Suits deliberately planted fradulent evidence to implicate his own firm in a cover-up. Events were such that blame fell on Jessice Pearce's shoulders, giving Hardman just enough votes to replace her as managing partner. Unfortunately for him, doing so cost each voting member $100,000 and when it was revealed he was the reason for that loss, the member unanimously fired him.
Once Upon a Time: Rumplestiltskin's plan to get to the "real" world and find his son ends up backfiring on him when he ends up trapped in Storybrooke just like everyone else, unable to leave lest he lose all of his Enchanted Forest memories- and therefore his memories of the very son he's there to find.
Bigger Bad Cora has spent decades manipulating, abusing, and scheming to satisfy her unquenchable thirst for power and desire to hurt royalty out of revenge for their shoddy treatment of her, a lowborn miller's daughter. This includes using magic to kill Snow White's mother in a slow and painful fashion. Snow White tries to save her mother, and Cora tricks her into taking a black-magic enchanted candle that will save one life by killing someone else. Cora intended to corrupt Snow White in the process. As a child, Snow cannot bring herself to use it and loses her mother. But when Snow White is an adult, has been tormented by Regina (Cora's daughter, and the Wicked Stepmother) for well over 30 years, realizing Cora killed her mother, being Forced to Watch as Cora and Regina murder her childhood nanny, and realizing Cora's got a scheme in the bag to achieve nearly godlike power by killing Rumplestitskin and gaining his power? Well, that candle does get used, Rumplestitskin is cured, and Cora's the one who dies by her own magic.
Dad's Army: In order to clear the rubble from a bomb-damaged pumping station, a process which will be very dangerous for the two people at the front, Captain Mainwaring puts pieces of paper in his hat and marks two with crosses to indicate who will be at the lead. When it comes to Private Frazer's turn, Warden Hodges rudely pushes him aside and takes a piece of paper instead. So of course, Hodges gets one with a cross on it.
Frazer: What a pity; I was going to take that one.
The Inspector Lynley Mysteries begins with the bureaucracy of Scotland Yard partnering the haughty, aristocratic Detective Inspector "Tommy" Lynley with the cranky, working-class Detective Sergeant Barbara Havers in the hopes that one or both of them would do something outrageous enough to justify sacking them (but preferably her). It didn'tquiteworkoutthatway.
On Baywatch, Stephanie is taken prisoner by an escaped criminal. Hiding in the back of her truck, he orders her to drive off the beach. When Mitch radios Stephanie to tell her to return to headquarters, Stephanie starts to say "I have a code—", but the man cuts her off, knowing full well that she could be naming a code that alerts Mitch to her situation. Instead, the man orders her to tell Mitch that she has found a lost child and is driving him around to find his parents. But as this violates lifeguard policy (which is to take the child back to headquarters), it ends up having the very result the man was trying to avoid—Mitch instantly realizes Stephanie's in trouble and sends the cops after her.
Banshee has a literal example. During the shootout in the season one finale, a group of Ukrainian gangsters try to use a rocket propelled grenade to kill the good guys. However, a lucky shot kills the guy carrying the rocket launcher and he squeezes the trigger while the rocket is pointed at a nearby wall. The explosion kills the other gangsters.
Series//Horrible Histories: At the end of the Greek "Historical Wife Swap", the Athenian man suggests they vote on whose way of life is the best. The Spartan man votes Spartan. His wife votes Spartan. The Athenian man votes Athenian. His wife... doesn't get to vote, she's only a woman!
In The West Wing episode "The Stormy Present", CJ lampshaded it almost word for word when she was handed the supposedly classified budget for DARPA, the creators of the internet, by Carol because it found ONthe internet.
Carol: The DARPA budget.
CJ: I thought it was classified?
Carol: Apparently not. I found it on the internet.
CJ: Hoisted by their own petard.
In season 4 of Arrested Development Gob plots to get revenge on his rival, Tony Wonder. First he says he's going to make Tony fall in love with him and then break his heart; when he learns that Tony's faking being gay for publicity he decides to ruin his reputation by tricking him into having straight sex on camera. Both plans rebound on him. He's tricked into having sex with Tony, on tape - just as he becomes President of the Bluth company and is warned to avoid any scandals - and in his completely hypothetical situation to Michael afterwards he implies he's actually fallen in love, only to later get a voicemail revealing Tony's roofied himself to remove the memory of the previous night.
Dead Like Me: In a non-villainous example, a flashback reveals that Roxy invented legwarmers and was strangled to death with her own invention by her jealous friend.
In the BBC/Starz series The White Queen, Queen Elizabeth (the consort of Edward IV, not the more famous daughter of Henry VIII) and her daughter, also Elizabeth, both threaten to lay a terrible curse (in this show, both Elizabeths are real witches, with real magical powers) on whoever killed the princes in the tower, the specific nature of which is that the killer's own firstborn son, and his grandsons, and all his male lineal descendants, will die. Of course, the show heavily implies that the killer was Henry Tudor, later King Henry VII, and husband to the younger Elizabeth. In other words, they just cursed their own descendants. Richard III, hearing their threat, even warns them:
Take care. Your curses last too long, and may turn on someone you love.
Fringe has Harris, the Obstructive Bureaucrat who's been trying to railroad Olivia out of Fringe Division and turns out to have been working in fringe science for quite a while. He's busted when he attempts to weaponize several latent pyrokinetics - and when Olivia shows up to rescue one of them, he locks her in the room with one who's going critical. If she can't direct the energy outwards, then she's useless to Harris's needs, and she'll explode, which will take Olivia with her. Olivia, however, manages to convince the pyrokinetic to focus the energy outwards. Guess who she focuses it on.
This happens a couple of times in the Breaking Bad finale. Jesse, having been held captive for months by Todd and Jack, strangles Todd with his handcuffs and breaks his neck. Walt catches a bullet from the machine gun he set up.
On The Blacklist, the titular villain from "The Stewmaker" specializes in using chemicals to dissolve the bodies of people killed by a drug cartel. Reddington tracks him down after he kidnaps Elizabeth and kills him by pushing him into his own tub of chemicals.