Bellamy has this reaction when he finds out that, because he kept the Ark from finding out Earth is survivable, they executed 300 people to reduce their excess population, rather than sending them to safety on Earth. When he does finally alert the Ark that they can survive on Earth, Kane (the man behind the mass execution) also has one of these, realizing that all the people he killed could have been saved if he'd only waited a few more days.
Clarke has one when she sees the aftermath of a missile attack that she could have prevented, but chose to let happen anyway. Lexa might have had this reaction, too, but being The Stoic, it's hard to tell.
Said verbatim in flashback by Becca when her AI creation Allie launches the nuclear war that wipes out humanity.
666 Park Avenue: Annie says this word for word when she realizes her way out of her deal with Gavin will lead to an innocent man's death.
The Carpenter has one in the Syfy miniseries Alice, right after breaking through his memory block and remembering his past life as Alice's father, then realizing it's a problem that he's spent the last ten years of his life sucking emotion juice out of people. Redemption Equals Death
Andromeda: In an alternate timeline Gaheris Rhade reacted this way when he realized his betrayal of the Commonwealth did not result in a better safer universe, but a lawless chaotic dystopia facing imminent doom.
The Andy Griffith Show: Opie goes through this when he kills a bird. He ends up trying to make up for it by raising her babies until they're old enough to leave the nest.
On the Angel end is Gunn's epic version of this after his part in Fred's death. He wanted to keep his super smarts and signed a paper saying that a delivery could be made to Wolfram and Hart. What he didn't know? The delivery was the tomb of Illyria, which was sent to infect Fred and brutally kill her so that her body could be used to host Illyria.
And Wes's equally epic one after he went literally Axe-Crazy in "Billy". He was under a spell, but it didn't matter, he still hated himself.
Wes also had one after he shot what he thought was his father in "Lineage".
Arrested Development uses a variation of this, "I've made a huge mistake." The phrase is used for comedic value, though. It was first said by GOB in "Key Decisions", and used by various characters afterwards, although it does remain primarily GOB's catchphrase, as he uses it at some point in most episodes.
On The A-Team: Face's expression after he pushes Murdock to the ground during their fight in Family Reunion borders on this. It's kind of a combination "What did I just do?" and confusion over the fact that Murdock doesn't seem the least bit angry with him for doing it.
Londo has several moments of serious regret as his schemes to restore Centauri power and glory play out... though that doesn't prevent him from going through with them until matters reach the point where Centauri Prime itself is at risk of annihilation.
The most heartbreaking instance may be when G'kar, his longtime nemesis, accepts an official apology from the Centauri Emperor for crimes committed against the Narns and approaches Londo in good spirits, extending a tentative hand of friendship. The problem: Londo made a deal with the Shadows only hours before that would result in another Narn-Centauri war. The look on Londo's face as he realizes his mistake is Tear Jerking.
Londo gets a lot of these moments. In the same episode, when the Centauri Emperor is on his deathbed, Londo tells him how the Centauri have attacked a Narn colony, kicking off a terrible war to further the Centauri's expansionist ambitions. The dying Emperor whispers his last words to Londo. Londo tells the other Centauri present that the Emperor told him that he would want them to continue, and to "carry my people back to the stars". But what did he really say?
Londo: He said... That we are both damned.
Another instance of this happening to Londo (Seeing a pattern?) made it into latter season's credits, with Londo watching the orbital bombardment of the Narn Homeworld with outlawed Mass DriversSee Here. (spoilers, obviously)
Also in that show is Delenn upon watching Dukhat die after being attacked by Earth Alliance warships orders their immediate destruction. "NO MERCY!" When she calmed down she was horrified to learn that her actions had started a full-scale war.
In the second season finale, Captain Sheridan gets one after he orders the station's defense grid to open fire on a Centauri cruiser in self-defense, resulting in the cruiser's swift destruction. Definitely justified, in that every action he had taken had been with the intent of protecting lives, rather than taking them, only for him to be backed up against the wall and only left with the one option. He has a similar reaction midway through the third season when he does the same thing... to an Earth Alliance destroyer.
The Expanded Universe reveals the Centauri had a collective one at the end of the Centauri-Orieni War, when, after ten years of war started by the Orieni getting caught trying to backstab them right as the Centauri tried to end their cold war peacefully, they are in the orbit of Orien debating if to accept the enemy's pleas for peace or launch an attack that would likely destroy the planet as a collateral damage of cracking its defenses... And the realization they and the Orieni already did so multiple times catches on them, prompting the Centauri to accept their enemy's surrender and even impose less harsh terms than what the Orieni were willing to accept, just as long as the Orieni renounced the mass driver technology.
Hugo has a moment of this after finding out that Sergio's biological parents were killed, as he's the one who encouraged them to properly meet with Sergio's adoptive parents Alma and Luis to iron out a suspicious guardianship situation.
Julia's turn comes upon discovering that helping a sick Manuela and a healthy Iván escape medical custody only resulted in the two of them being found anyway and Iván getting infected in addition to Manuela.
Pedro gets very loud slap from the nurse caring for him for breaking the rules by interacting with his father. His father is leaving the scene and can't turn back without getting into more trouble, but close enough to hear the incident. He's clearly made uneasy by the fact that interacting with his son resulted in him getting hit by one of his wardens.
In Battlestar Galactica, Gaeta, during the mutiny on Galactica in Season 4. After Gaeta helps Zarek take over Galactica, Gaeta insists on giving Admiral Adama a court-martial for conspiring with the Rebel Cylons. But when Zarek has the Quorum of Twelve gunned down for refusing to recognize him as President over Laura Roslin, Gaeta has a bit of a revelation while looking over their dead bodies.
Sharon (Boomer) has a change of heart when she sees the experiments being done on Athena's daughter.
Baltar learns that he gave the Cylons information that helped them to kill billions of people.
The originalMy God, What Have I Done? moment, when Boomer finally 'regains consciousness' and sees the aftermath of her actions in the Season 1 finale. And the thematic continuation, the Season 4 premiere has Tigh experience a sort of 'waking nightmare' where he imagines the consequences of not owning up to the horrible truth of what he believes himself to be — killing Adama — and is horrified by the thought.
Battlestar Galactica (1978) in its premiere episode has President Adar moaning at how his gullible stupidity falling for Baltar's manipulations has led to the destruction of humanity, even as the Cylons are wiping out the fleet.
Being Human (US): After learning she unwittingly killed her own son, Suzanne brokenly screams in agony over his body, vowing to stop any other vampires from harming humans as best she's able later.
Legarski shows genuine horror at learning he killed two people and sex-trafficked women, since he forgot all about it due to brain damage.
In Blackadder Back & Forth, Blackadder is clearly horrified when he discovers that he's altered history and caused Britain to become a French colony. It's implied that he could have lived with Robin Hood and the works of Shakespeare being erased from history, but he ends up restoring everything back to the way it was (for a few minutes, at least).
In a Very Special Episode of Boy Meets World, Shawn has taken to drinking. His friends confront him and try to convince him to stop, citing his family history of alcoholism, but he rebuffs all their attempts until he shoves his girlfriend Angela into the door in anger. He is immediately appalled at this last action of his, even gasping "how did that just happen?" in horror afterwards, and it causes him to immediately stop drinking and seek help.
Jesse becomes depressive after shooting Gale. He also blames himself for the heroin overdose of his girlfriend.
In "One Minute", after a deception allows Walter and Jesse to elude him, Hank is enraged to the point of severe Police Brutality against Jesse. After he calms down, he is visibly horrified at his actions.
In "Ozymandias", after nearly five whole seasons of rationalizations and selfish justifications, Walter finally goes through an absolutely gut-wrenching one after kidnapping his baby daughter when he runs away from his wife and son after they turn on him. While he's taking care of her in a restroom, she says "Mama" and realizes, in that moment, that his actions over the course of the series have led to the destruction of his entire family, either through death or ruined lives. He tearfully has a phone conversation with Skyler where he acts like an abusive husband who threatened her to cooperate, in order to exonerate her to the police as well as to break ties with his family and leaves Holly at a fire station to be returned to Skyler.
Faith does this twice. First when she accidentally kills Alan Finch, screaming repeatedly "I didn't know!", and when she remembers what she did to Wesley and Buffy.
This is also plainly evident in Willow's expression in "Once More With Feeling" when Buffy lets the Scoobies know that when they brought her back to life they pulled her out of Heaven.
Spike after the Attempted Rape in "Seeing Red". In a rather disturbing take on the trope, he seemed almost as distressed about his inability to go through with the act as he was by the fact he attempted it at all.
Spike: "What have I done? ... Why didn't I do it?"
Spike, as a soulless vampire, isn't supposed to have a conscience and therefore feel bad about his actions. His existential crisis over not being good but no longer truly being evil, shown in his version of the trope, is what prompts him to go and win his soul from a demon in Africa.
Angel after the gypsy curse personifies this trope. He now believes he has to atone for what he has done.
Buffy has this twice, once in "Dead Things", when she learns that she didn't come back wrong and has been doing all sorts of horrible stuff of her own free will, and again in Season 8 when Giles is killed, magic is destroyed, and the Slayer line is ended, as a result of her space frak with Angel.
Angel, after his soul was restored. His soulless, sadistic alter ego having tried to kill Buffy multiple times, murdered Giles' girlfriend, brutally tortured Giles, feeding off of and killing numerous people off screen, and ALMOST banished the entire population of Earth to hell, he was so wracked with guilt that it eventually caused the decision to leave Sunnydale forever, which in turn began his own spin-off series.
Chapelle: I'm like, you can't say skeet on the radio! You know what's so dope about skeet? White people don't know what it means yet. When they figure it out, they'll be like My God, what have we DONE?!
In the Charmed episode "We're Off to See the Wizard", Phoebe utters this almost verbatim after using pyrokinesis — an upper-level demonic power — on Cole's new personal assistant.
Cheers. Carla once asked Frasier: "When you and Lilith wake up in the morning, which one of you is the first to scream, 'My God, what have I done?!'"
In another episode, this is essentially Fraiser's reaction upon fully realizing that he has successfully launched Woody Boyd's political career. (Cue visions of atomic fireballs.)
In Season 1, Diane goes through a non-verbal version of this, after Coach and the others convince her to throw a baseball down the hall into the pool room, where Coach is standing. It Makes Sense in Context — Coach is proving a point to her about his uncanny success at bunting... with his noggin. It's even worse for poor Diane when you consider that she fully expected to miss — but as Sam notes, that's part of the point.
In The Closer, after several episodes of not feeling any remorse for facilitating a Vigilante Execution the previous season and not taking the victim's family's lawsuit against the department seriously, Brenda finally breaks down sobbing "What Have I Done?" at the end of Season 7 Episode 5, after everyone in her unit, plus Chief Pope, Commander Taylor, and her husband are all subpoenaed.
Natalia is seen crying in the toilet because she knows that she had betrayed her best friend Isabela by being an accomplice to the hacker's bidding.
Gerry is horrified when his punch puts Luis into a coma, and even more after Luis' death.
Alex is horrified that one innocuous act she did led to Luis's death inadvertently. That's what motivates her to pursue revenge on his behalf, acting out Luis's violent fantasies.
Brass had one in the CSI episode "Genetic Disorder," after spending the entire ep assuming Doc's wife really had cheated on him.
In another episode, a husband and wife kill their baby after he starts showing symptoms of the same degenerative disease that killed their first son. They find out after it's too late that he was simply sick because of the pesticide his mother used in the garden, and if she had stopped using it, he would have been perfectly healthy.
A girl who survived a car accident is found murdered in her hospital bed. It turns out to have been by the mother of her friend who was outraged at the accident killing her daughter. Mac has to break it to her that because of a mix-up at the scene, the girl in the bed was the woman's daughter. She remembers her waking up under her bandages to ask "Mom?" but she assumed it was the friend asking for her own mother. The woman is completely destroyed to realize her daughter died not knowing why her mother was doing this as Mac notes, nothing the courts can do can be worse than what the woman is already going through.
In one episode, a joke shop owner named "Laughing Larry" is the target of a murder attempt via a lethally-powerful exploding cigar. When confronted by the killer, the man relates how, as a child, he and his best friend bought a cardboard 'submarine' from the shop owner, and his friend, Sam, was the first to try it out in a pond. Larry is initially pleased at the story of some children enjoying his products, until...
Benjamin: Sam knew that it would work, because Laughing Larry said would work, so why wouldn't it? You know, what you forgot to tell us is that, uh, that Sam had to know how to swim. Larry:[Goes from smiling to staring in horror]
Also the reaction of the would-be assassin in another episode when he's told the gun he threw in a dumpster after his failed attempt was found by two kids...one of whom accidently shot the other to death with it.
Also that of Frank Waters, an ex-colleague from Jo's FBI days, when he realizes that his attempt to finally nail a serial rapist results in the death of someone else.
Delete: The AI reacts this way after uploading Daniel's mind, and seeing its actions through his conscience.
"The End of the World": The Doctor has a comparatively mild one when, after taking Rose on her first trip to Platform One, five billion years in the future, and playing up the bizarre guests and conventions, he realizes he may have been a bit hasty when he sees her stagger out in the middle of a culture shock breakdown.
Rose doesn't learn that the version of The Weakest Link she's wound up on is lethal until she sees a woman she voted out get vapourized right in front of her.
The Ninth Doctor has this reaction when he looks down on a ruined Earth, populated by people who do nothing but watch horrific game shows and realises that it all happened due to his actions earlier in the series.
The Ninth Doctor again, when he forcibly sends Rose back to her own time in the TARDIS to protect her from the Daleks, only for her to absorb the power of the Time Vortex itself to get back and save him. He is truly distraught as it threatens to burn up her mind: "The power's gonna kill you, and it's my fault!" He sacrifices his Ninth life to save hers.
"Evolution of the Daleks" gives one to Dalek Sec. After becoming a Half-Human Hybrid, he comes to realize just how horrific the Daleks' wars for supremacy have been, and attempts to atone. Unsurprisingly, the rest of the Cult of Skaro doesn't take well to this and turns on him, eventually resulting in his death.
"Forest of the Dead": The little girl gets this when she snaps at her father and makes him disappear with her TV remote. In response, she hurls the remote to the floor, activating the Library's Self-Destruct Mechanism.
"Midnight": After the hostess sacrifices herself to save the Doctor by throwing the possessed Sky out of the cabin, all of the other passengers seem deeply shaken by how monstrous they became in the face of the unknown entity. When the rescue arrives, all of them are sitting around quietly looking ashamed.
"Journey's End": The Doctor looks rather stricken when he finds out that Harriet Jones, the former Prime Minister he deposed, robbing Britain of its Golden Age, sacrificed herself to get him to Earth anyways.
"The Waters of Mars": The Doctor saves people whose deaths will trigger the Golden Age of space exploration. He realises the impact of his interference when the key survivor realises what has happened and kills herself. The Doctor is subsequently horror-struck and has a massive Heel Realization.
"The Beast Below": Liz 10's reaction when she discovers that the Star Whale serving as the engine of Starship UK was captured and tortured on her orders, and she's been resetting her memory every ten years for centuries so she can remain innocently ignorant of this fact.
Amy herself has one at the end of "The Impossible Astronaut", when she shoots someone in a spacesuit who retracts its visor to reveal a little girl.
The Eleventh Doctor had one in "The God Complex". A beast attacks his friends, and the Doctor thinks that it feeds on fear, so he tells them to focus on their faith. More people die much more rapidly after that, and Amy, his companion, is particularly affected. The Doctor realizes that the monster doesn't feed on fear, but on faith. Since Amy basically sees him as a God, it's her adoration for him that will kill her. He breaks her faith with a Zero-Approval Gambit and unceremoniously drops her off at her house, planning to never speak to her again.
The Twelfth Doctor has two in Series 9, both related to the season's Story Arc.
First, he has a downplayed example in the denouement of "The Girl Who Died" as he ponders the possible consequences of his rash decision to save Ashildr's life in a way that might — and does — render her a functional immortal. As it turns out, this paves the way for her betraying him and capturing him for the Time Lords — which inadvertently leads to the death of Clara Oswald, his beloved companion in "Face the Raven" near the season's end, whereupon he's subjected to Cold-Blooded Torture, has a massiveSanity Slippage, and...
In "Hell Bent", the Season Finale, he decides to risk the safety of the entire space-time continuum on a Tragic Dream: saving Clara from her fixed-point death. At first, it looks like nothing and no one can invoke a Heel Realization in him, but when Clara objects to his intent to mind wipe her, he finally, sadly asks "[W]hat am I doing?" and chooses to return to his best self, allowing Laser-Guided Karma to have its way with him because he knows he deserves it for becoming The Unfettered.
In addition, Clara Oswald herself has two moments like this in "Hell Bent": First upon realizing her mistake on the trap street led not just to her death, but his insanity and much of his suffering, second when she watches him get mind wiped with a device she tampered with to save herself from that fate.
Companion Bill Potts gets this in "The Lie of the Land". At the end of the previous episode, she made a Deal with the Devil in order to save the Doctor's life, because she thought the Doctor would be able to save Earth from the villains: it didn't work, as he has been brainwashed by the villains, meaning saving the day is down to Bill. Even after it turns out the Doctor was faking it, she feels that she is the only one who can save the world, since she was the one who doomed it in the first place.
Topher: An entire army in a single instant; that's all it takes. That's brilliant!Why didn't I think of that?(sees Adele's expression) Did I think of that? Did I? Oh god... oh my god... oh my god...
Miss O'Brien from Downton Abbey is usually an unrepentant Jerkass, but when she deliberately places a bar of soap so that Cora will slip on it, hoping that Cora will miscarry and be forced to keep employing her, she looks at her reflection in the mirror while waiting for Cora to get out of the bath and says "Sarah O'Brien, this is not who you are." After Cora is injured and miscarries, it's even worse.
The final stroke is when, at the garden party, the Dowager inadvertently reveals that Cora was never thinking of getting rid of O'Brien the poor woman is left pale and stunned, standing there realizing all she did was based on miscommunication.
In one episode of the fifties run of Dragnet, the man who molested two four-year-old girls is horrified by what he's done.
The Dukes of Hazzard: Comedically, in "The Late J.D. Hogg". It's the classic "two weeks to live" episode after Boss Hogg is told by his doctor he has a terminal illness. Boss does a good job repenting for a life of sin ... until he is told his diagnosis was in error and that he is healthy. He then sees all the good that he's done and all the mistakes he's made up for ... (gasp) "What have I done????!!!!????" (He then, needless to say, spends the rest of the episode trying to undo all the good that he's done.)
Family Ties: In the second season episode "Uncle Ned", after Ned (Tom Hanks) comes home drunk — even drunker than when he went to his job interview — he gets into a huge argument with the family over whether he has a problem. He eventually gets into a struggle with Alex and accidentally punches him ... setting the trope in motion and forcing Ned to finally realize he has a problem.
A 'My God, what have YOU done' moment happens at the end of the Peacekeeper Wars in Farscape. For four years people have been chasing John Crichton, killing, raping and attacking him and his friends for his wormhole knowledge, and he finally gives in and builds the thing to protect his wife and newborn child, and it turns out that wormhole weapons he's been telling everyone are horrific, galaxy destroying weapons that no one should ever have under any circumstances are actually just as bad as he always said they were. When he turns it on, even those most desperate to have them realise just how bad it is.
[the wormhole weapon has been fired, and threatens to consume the entire universe] Crichton: Here's how it lays out. Are you listening Stahleek? Grayza? Wormhole weapons do not make peace. Wormhole weapons do not even make war. They make total destruction, annihilation, Armageddon. People make peace." Chiana: Crichton, can you stop it? Crichton: I don't know, Pip. Maybe it eats the whole galaxy, a monumental black hole, a giant whirling headstone marking the spot where we all used to live and play and slaughter the innocent. Scorpius:[softly] This is insane, Crichton. [John lets out a choked laugh] Crichton: God! Four years on and you're finally getting that!
A far more literal example is when Crichton has been forced to kill Aeryn while possessed by the Neural Clone. In this case, Crichton really does say "My God, what have I done?"
In Fate: The Winx Saga, upon learning that the people of Aster Dell were blood witches, Silva is horrified that he (supposedly) killed Andreas for no reason.
Forever Knight's Nick Knight has several of these over the course of the series, many in the flashbacks where he's struggling between needing to feed to survive and not wanting to kill.
Will's reaction from the middle to the end of The Fresh Prince of Bel-Air episode, "Just Say Yo...", especially after a tearful and utterly remorseful Will admits to the family that the drugs that nearly killed Carlton was his, but that he had been given them by someone else due to the stresses he had with his job, school and sports wiping him out and just put them in his locker.
Also played for laughs in Friends: Chandler has his "nubbin" removed after a squicked-out date leaves him. He misses an obvious joke, then cites the nubbin as the source of his "powers." He then says "Oh dear God, what have I done?"
And it's played for laughs in Full House during the episode "Three Men and Another Baby", when Stephanie reluctantly gives Mr. Bear to Michelle, she philosophically claims it was worth it to make the latter happy, but no sooner does she say that does she leave the room and exclaim, "What have I done?!"
Theon Greyjoy silently has this reaction after looking back at everything he has done, taking Winterfell, killing two orphan boys, then passing off their burnt corpses as those of Bran and Rickon. All because he wanted his father's approval, but for him, he already died in King's Landing.
This is written all over Ser Loras Tyrell's face as he sits near the corpse of King Renly Baratheon. He feels extremely guilty for convincing his lover to make a bid for the Iron Throne, as this path led to Renly becoming a target for assassination.
Catelyn admits that she regrets having refused to love Jon Snow and treat him like a son and believes that the misfortunes of her family are the gods' way of punishing her.
Although she blames Joffrey and Cersei for it later, Arya is horrified when Cersei demands Sansa's direwolf Lady is killed in Nymeria's place.
Bran has this reaction when he realized that he unintentionally destroyed Hodor's mind.
Hodor's reaction upon realizing that Bran used him to kill somebody.
As Joffrey rises to ever new heights of cruelty and perversion, Cersei finally acknowledges that having three inbred children with her twin brother wasn't such a great idea — considering what it did to the Targaryens — to say nothing of putting the most unstable of them on the Iron Throne itself. She breaks down in tears from the sheer knowledge that the son she loves (despite everything) is a psychopath. Nevertheless, in later episodes, she undergoes a mild Selective Obliviousness.
The Hound has this reaction when returning to the farm from Season 4 only to find that the old peasant and his daughter killed themselves so they wouldn't starve to death. He is immediately broken with guilt for having stolen from them and proceeds to bury their remains.
In "The Laws of Gods and Men", after being confronted by the devastated son of one of the Meereenese nobles whose crucifixions she ordered, whose tirade against Daenerys verges on a Breaking Speech for her. Afterward, for all of Dany's slave-freeing, vigilante queen bravado, she looks and sounds utterly disgusted with herself.
Hizdahr zo Loraq: My father, one of Meereen's most respected and beloved citizens, oversaw the restoration and maintenance of its greatest landmarks. This pyramid included. Daenerys: For that, he has my gratitude. I should be honored to meet him. Hizdahr: You have, your Grace. You crucified him. I pray you'll never live to see a member of your family treated so cruelly. Daenerys: Your father crucified innocent children. Hizdahr: My father spoke out against crucifying those children. He decried it as a criminal act but was overruled. Is it justice to answer one crime with another?
She feels a million times worse when a goat-herder cries as he presents her with the charred skeleton of his daughter who was burnt alive by Drogon.
He immediately feels remorse for killing Shae, and he is clearly upset while he's strangling her.
In Spoils of War, Tyrion reacts with horror upon seeing Lannister soldiers being burned alive by Drogon and slaughtered by the Dothraki all as a result of Dany following his advice to lay siege and encircle the capital with her army rather than using her dragons to take over.
After being repelled at Blackwater Bay, he has a brief Crisis of Faith during which he exhibits sudden regret for leading men to a horrible death and for having killed his own brother. Whereas before he considered Renly collateral damage for opposing him, he now considers it straight-up murder.
Stannis: I fought for your god in Blackwater Bay. I led my men to the gates of the Seventh Hell as their brothers burned alive and for what?! [...] I murdered my brother! Melisandre:We murdered him. Share the weight with me. Stannis: He wasn't your brother.
He falls into this again after Shireen's sacrifice. By the end, his typical stoic glare becomes a Thousand-Yard Stare and he looks dead inside.
Selyse breaks down out of guilt at the sight of Shireen being burned and commits suicide soon afterward.
General Hospital's Luke Spencer says this verbatim after raping his beloved Laura.
In the Get Some In! episode "Medical", Drill Sergeant Nasty Corporal Marsh tells the aircraftmen under his instruction that they could all be dismissed from their two years' National Service if one of them commits suicide. When AC2 Leckie comes in from being punished for making a few mistakes during drilling (having thus missed the earlier conversation), he says he would shoot himself if he had any ammunition for his rifle. The other airmen are intrigued by this and almost seem to egg him on. However, later that evening, they find Leckie and his rifle have vanished, and soon Marsh appears demanding to know why a round of live ammunition is missing from the armoury. The aircraftmen are left reflecting with horror on their inaction and even encouragement toward Leckie's suicidal thoughts... until he returns from a visit to the armoury where he learned how to avoid the mistakes for which Marsh punished him, and explains that the missing round of ammunition was just an arithmetic mistake.
On Glee, when Sue goes into a deep depression, Will has a silent version of this, after a mild What the Hell, Hero? from Kurt.
Good Luck Charlie: In The Movie, Amy didn't realize that accusing Teddy of ruining Christmas would hurt Teddy's feelings. Teddy breaks down crying and walks away from Amy.
The Great British Baking Show: Invoked rather humorously by Season 6 contestant Nadiya when she's describing an extremely ambitious and technically demanding project she's about 1/3 of the way intonote The project is a "floating" cereal treat soda pop can pouring fruit soda buttons onto a citrus cheesecake. She invokes the trope when it finally dawns on her how unnecessarily complicated her plan is, and has no time to start over with anything else.
Nadiya:[laughing nervously] Oh my God, what have I done!?
In the second season, Nick is forcibly assigned a teenage wife named Eden and ends up taking out a lot of his resentment over the situation on her, despite her genuine attempts to make the marriage work. This ends up going very badly. Eden eventually falls for another man, a Guardian named Isaac, and the pair attempt to elope so that they can have a chance at real love, only to get caught and forcibly dragged back. Nick feels horrible realizing that his actions have contributed to an innocent teenage girl losing her life, and while he desperately tries to convince her to "confess" in the hopes that she will be spared, she refuses to allow herself to lie to Godand instead recites a Bible verse, shortly before the government executes her.
After the above example, most of the Waterfold household gets this to an extent as well. It contributes to June's decision to get her newborn daughter out of Gilead before the same thing happens to her.
In Season 4 of Heroes, Samuel has this reaction after murdering his brother, Joseph. He may or may not quote this trope by name, as Robert Knepper's well-done emotional performance makes it unclear whether he's saying "What have I done", or if he's begging Joseph to "Hold on".
Duncan on Highlander after he killed Richie in a demon-induced haze. His distress is so extreme that he immediately asks Methos to kill him.
House didn't say it out loud, but his facial expression clearly said it after he punched Chase in the eye in one episode.
House of Anubis: Fabian has a moment of this, repeating "What have I done... what have I done?", when accidentally checkmating Nina during the Senet game, and getting her sent down into, at the time, nobody knew where. Throughout the next episode, he got increasingly desperate and panicked over her disappearance until he eventually had an actual breakdown, one of the bigger Tear Jerker moments of the second season.
iCarly: Freddie utters this line as a group (What have WE done?) when the gang realized that bringing back Marta made Lewbert's life even worse.
Carly went into a breakdown of repentance in "iChristmas" when her wish turned her life into one she did not want.
Freddie again evokes a variation of this trope in the extended version of iSaved Your Life. After his break-up with Carly, his face changes expression while in the elevator and asks himself in regret, "What did I do?" Cue a zoom out of the Bushwell building as Freddie yells "WHAT DID I DO?!"
Spencer in the flashback of "I Get Pranky" upon realizing his prank truly hurt his classmates
Innocent: Tarık has a breakdown after he believes he has killed his wife Emel during an altercation. Unable to cope with what's happened, he calls his brother to deal with the problem, which only makes matters worse.
Intergalactic: Ash is distraught after her summoning Commonworld to arrest Grieves results in their soldiers killing Candy's mother. She is nearly Driven to Suicide over it.
Kingdom (2019): Yeong-shin has this reaction after feeding the villagers with human meat, since it ended up turning almost everyone in the village into zombies.
Law & Order: UK. Jamal Clarkson, who shot DS Matt Devlin in order to avenge his brother's murder, completely breaks down when Matt's partner Ronnie makes him understand that Matt wasn't a racist and had nothing to do with the botched investigation into his brother's death, meaning that he's not only failed in his mission, he's killed an innocent man.
Lip Service: The driver who struck Cat accidentally had this reaction, becoming so distraught the hospital staff had to sedate him.
In Lost, Jack has this reaction after finally escaping from the island.
"We have to go back!"
Kamen Rider Build: The expression of absolute, mind-shattering horror that Sento gets upon realizing he killed another human being is one of the most haunting moments in the story. He was desperate enough to use the Hazard Trigger despite being terrified of its effects. It gets more power out of the emotion-based Rider system by overstimulating the user's brain, which inevitably ends in a state of mindless rage in a matter of minutes.
In M*A*S*H, Father Mulcahy once impulsively punched out an unruly patient who hit him first during triage, when any delays in the selection process can cost lives. While the rest of the staff agree he was entitled, Father Mulcahy was kicking himself for some time afterward.
Hawkeye has this in the episode "Fallen Idol". He sends Radar to Seoul to "sow a few wild oats", and Radar subsequently gets wounded by enemy fire en route.
In the episode "O.R.", Frank Burns complains out loud about the difficulty he's having removing a wounded GI's kidney. On a hunch, Trapper goes over to look at the patient's X-ray... and shows Frank that the guy only has one kidney. While Frank's borderline incompetence in surgery is usually Played for Laughs on the show, in this instance he's shown to be genuinely shaken at the realization that he could have killed the man through his carelessness.
In the Merlin (2008) series, Arthur goes into this trope after killing a captured rival king in "His Father's Son".
Later in the series Guinevere is given an enchanted bracelet that rekindles her feelings for Lancelot and leads her to make-out with him on the eve of her wedding to Arthur. They're caught, and the trope is played out in a truly heart-rending manner. Since Gwen never discovers that she was enchanted, she honestly has no idea why she betrayed Arthur — she didn't want to, and she can't understand why she did. The question: "what have I done?" is taken quite literally.
Riley has this reaction in the opening scene of the miniseries, which shows the crash he caused by driving drunk. When he realizes he killed the young driver of the other car, he's horrified, and he immediately pleads guilty and accepts the judge's sentence.
In the final episode, once the bloodlust and mob mentality wears off, the vampiric townsfolk are horrified by the carnage they've inflicted; in particular, a traumatized Ooker confesses to Sturge that he's pretty sure he killed his own mother.
NewsRadio: In the episode "Who's The Boss (Part 1)", there's a scene where Beth is trying to fix the coffee machine (due to Joe the Handyman being on strike) while Dave (who is known to be a coffee addict) nervously waits for it to be fixed so he can have his cup of coffee. Beth believes she finally found what's wrong, but she instead causes the machine to short circuit, making the problem even worse. In horror, Dave shouts to Beth "My GOD, woman, what have you DONE?!"
Night and Day's Alex Wells during the final episodes, on discovering that he slept with his own daughter.
Olive gets hit with this in "Party of 5, 4, 3, 2, 1" when Otto manages to figure out that she is the countdown crook they have been looking for, and has inadvertently prevented everyone from counting down due to wanting to complete her New Year's resolutions.
In "Agent Oksana's Kitchen Nightmares", Oprah refuses to bend to Oksana's wishes for things that initially make the Food and Beverage worker seem greedy and selfish, like two hundred bars of gold, rose petals (each one individually plucked), a bag of diamonds, and a helicopter. As a result, Oksana ends up closing the Breakroom off, leading Olympia and Otis to take her place as Precinct 13579's Food and Beverage workers. However, due to their inexperience in the department, they can't keep up with their duty of refilling various appliances with food and Headquarters begins to fall to shambles, causing Oprah to feel regretful as she realizes that the precinct can't operate properly without Oksana and caving in to her demands. As it turns out, Oksana didn't want the items for herself — rather, she wanted the items in order to make special food for the precinct.
In "Total Zeroes", Sister Zero has this reaction when she becomes Drunk on the Dark Side and goes wild with her new power to multiply things by zero, leading to her eventually zapping her and Brother Zero's Supervillain Lair. She's in such a rut that she has no choice but to turn to Oprah for help.
In "Olympia's Day", Olympia gets hit with this when she goes completely off the rails due to Sanity Slippage and has a Freak Out, hallucinating and eventually blacking out. She wakes up some time later in Dr. O's office, where she is told that she has slipped into "mathness" and finally confesses to Oprah her Fatal Flaw of being unable to say "no" to others.
Root has this reaction in "/" when she realizes that the man she's been tasked with protecting is only in the position he's in after his life was ruined by the deaths of his best friends... deaths that were actually murders committed by Root.
Root: And the punchline, is that your Machine keeps telling me to save Cyrus. How badly did you have to break it to make it care about people so much?
In what she thinks is another of the endless VR simulations by Smaritan, Shaw is shown a woman who will develop a virus that will kill thousands in the future. Tired of these "lessons", Shaw takes a gun and shoots the woman dead. In her captive bed, she sees news coverage of the scientist's murder and how her hand is still bleeding from a cut and realizes to her horror, it was no simulation, she really murdered an innocent woman.
In the first season, Tommy has one immediately after Rita's spell is broken. It is probably justified because he should be going into shock.
Ransik says this in Power Rangers Time Force, when his obsession with revenge on all humans causes him to hurt his daughter, the only person in the world he loved. In fact, he loved her enough to end his quest for vengeance after harming her.
Nate of Power Rangers: Beast Morphers is absolutely horrified when he finds out he created Evox, even more so with the fact that Evox is a reincarnation of Venjix. It takes bringing Dr. K over to rattle him out of his Heroic BSoD.
The Pretender: during his captivity in the Centre, Jarod was used to run simulations for a variety of purposes, often being told his solutions would save lives. In the first episode, he says he broke out because he found out his work would be co-opted to hurt people if the price was right. He yells at Sydney and condemns the Centre for countless deaths, but he also blames himself because he thought up these "solutions" in the first place. He also has this exact reaction in "Past Sim" when Centre operatives use a hostage rescue scenario he devised to abduct a murder witness and kill a federal agent.
During "Back to Reality", Kryten has one when he thinks he's killed a man in self-defense, strong enough to drive him to consider suicide. Which was because he and the others were in a hallucination designed to push them to that point.
Lister, in "Tikka to Ride", asks this when he realises his maniacal obsession for a curry has completely smegged up history. Unfortunately, his accomplice in this is Kryten's spare head with his behaviour protocals removed, who doesn't get that it's a rhetorical question.
Lister: Kryten, what have I done? Spare Head 2: Well, sir, you've brought the human race to the very brink of extinction. Gum?
This is what separates the Chairman in RoboCop: The Series from the other heads of OCP/Omnicorp in the RoboCop franchise: the OldMan, the CEO, the Old Woman, Damian Lowe, Sara Cable, and Raymond Sellars don't care about other people and are only out for themselves. The Chairman, while greedy and willing to rush products without fully testing them, does have empathy, and is willing to recall products and make things right when he learns his actions and/or the actions of others at OCP have hurt people.
RuPaul's Drag Race often invokes this trope in the reunion episode, filmed after the season airs. Once the contestants watch the show and see themselves the same way others see them, they're often aghast at how bitchy they sound, and they make it clear that they did not intend to come across that way (this reaction is actually pretty common for reality tv).
Jerry Seinfeld, after he gets engaged to Jeanie Steinem, a woman exactly like him...
I think I may have made a big mistake! All of a sudden I realized what the problem is! I can't be with someone like me! I hate myself!
Another example occurs in "The Maid" when, after sleeping with Jerry, Cindy picks up her "maid" money and leaves, without actually having done any housecleaning. Jerry does a quick double-take and then asks Kramer, "What did I just pay for?" Kramer says, "Oh-oh. You're a john."
Clark is completely devastated when he realizes the explosion he caused inadvertently led to his mother having a miscarriage. To say he experiences a Heroic BSoD doesn't even cover it, and he proceeds to go on a "drug"-fueled rampage through Metropolis for three months in a desperate attempt to escape his guilt.
More seriously in "Identity", Chloe Sullivan's horrified expression after under the influence of Brainiac, she renders the bad guy of the week catatonic by overloading his brain with information to protect Clark.
"Stiletto", when Chloe dumps the body of the gangster Doomsday killed when he attacked her. She does this a lot...
And in "Sacrifice", Zod's reaction when he killed Faora. Along with her unborn child.
Stargate SG-1: Replicator!Carter seeks Carter's help to prevent a replicator army from invading Earth's galaxy, which has become immune to the Ancient disruptor. Carter trusts her because she believes no-one with her personality could ever work with Fifth. It's the only thing she's right about. Replicator!Carter's plan is to gain immunity to the disruptor, destroy Fifth, distribute her immunity to the replicator army she's now take control of and establish a foothold in Earth's galaxy. Carter's shocked reaction is 'What have I done?'.
Stargirl (2020): In the season 1 finale Yolanda immediately regrets killing Brainwave (even if it was in sef-defense) and her subplot in Season 2 focuses on her dealing with her feelings about it.
In "Galaxy's Child" this is basically Picard's reaction when he discovers that an alien lifeform was fighting back so hard only because she was defending her unborn child.
We're out here to explore, to make contact with other life forms, to establish peaceful relations but not to interfere. And absolutely not to destroy. And yet look at what we have just done.
Kevin Uxbridge from "The Survivors", who is really an immensely powerful being called a Douwd. Upon learning of the death of his wife at the hands of an invading alien race called the Husnock, he snapped and annihilated the entire Husnock species in one strike. Already deeply pacifistic, he was horrified beyond belief at this act of violence, and swore to live in exile for the remainder of his life, accompanied only by a facsimile of his wife and their homestead as a reminder of what he lost and what he did.
The episode "In the Pale Moonlight" is wholly dedicated to it. Sisko gives an account of his part in Starfleet's plan to deceive the Romulans into joining the war against the Dominion. Sisko damns every amoral action he takes to carry out the plan, which drags a neutral power into war and will cause the death of thousands or even millions who would have lived. Partially averted at the end where he declares that while he feels terrible for what he's done it had to be done and that he'd do it again.
Played for Laughs in the episode "Necessary Evil" when Rom walks in on someone trying to smother Quark with a pillow. His shrill shrieks get Odo and the rest of security's attention and Odo, getting him to calm down, tells Rom that he saved his brother's life. Rom feels proud of it... until he realizes that that means he isn't getting the Bar, causing him to shriek again. And on the med bed, Quark lets a shit-eating grin form on his face.
In one episode, Torres utters this exact line when she realizes the race of robots she is helping were responsible for the extinction of their creators.
Another was the Doctor realizing that he had disregarded his medical training and chosen to save his friend instead of someone he barely knew in a crisis situation. Being a medical program with a vast amount of ethical programming, he enters an almost literal Heroic BSoD over the matter. To be clear: There was no difference between the two cases from a medical standpoint, but he could only save one and he had to make a snap decision; it wasn't that his ethical programming failed so much as that he had never been programmed in how to make a decision where there was no obvious logic to indicate a correct choice (or, in fact, a clear correct and incorrect choice at all). He didn't actually do anything wrong, he had the reaction because he couldn't cope with having made a life-or-death decision based on something other than strict medical ethics.
In an episode of Strong Medicine, a boy comes into the hospital after having a police officer use a Taser on him. (They later find out that the only reason he reacted so badly was because of mercury poisoning.) Lu then spends the entire episode going into an Ideological Screed against the female cop. Later on, another boy comes into the ER, with the same cop. She mentioned that she was chasing him and reached for her Taser, but hesitated. Lu began to praise her (and herself) for this, but then the cop mentioned that, because she hesitated, the boy ran out into traffic and got hit by a car.
The Suite Life of Zack & Cody, Maddie in the episode Rumors was upset that London spread a rumor about her getting back together with one of her ex-boyfriends and told a reporter out of frustration that she has a fox's fur coat in her closest. However, after seeing the magazine with London of being an animal hater, Maddie realized the mistake she made and didn't tell her that she was the one who talk to the reporter. Although, out of guilt for her actions, Maddie told London the truth and they not only worked things out but also helped her resort her image.
Kara: (sobbing) It was so horrible, Alex. It was so bad, it was so horrible. Every bad thought Ive ever had, it just came to the surface. I couldnt stop it. I didnt mean it. I didnt mean what I said to you. Im sorry Im sorry for what I said.
Each of the major characters in Supernatural have this reaction at one point.
Sam after he finds out that by killing Lilith, he actually released Lucifer, and that him drinking demon blood didn't actually increase his powers — it was simply a Magic Feather that Ruby used to control him.
Taken: In the final episode "Taken", Mary Crawford has a breakdown after she receives a posthumous video mail from Dr. Wakeman, whom she murdered the previous day. She comes to regret her heinous actions and even seems genuine when she apologetically tells Charlie that there is nothing that they can do to prevent the aliens from taking Allie.
Timeless: When she returns to the present, Lucy is delighted to find her sick mother is now quite well. She's then horrified to discover that, because of her actions in the past, her sister Amy was never born.
Nora from The Thundermans has a "What did I almost do?" moment after almost hitting her baby sister with her laser eyes. She wants to give up her superpowers in the process
Even Jeremy Clarkson utters one of these in Top Gear. During the auction at which the trio bought their cars for the classic time-trial rally in Mallorca, he ends up overbidding for an Austin-Healey Sprite and only realises that he has to spend some of his own money on top of the initial budget after the auctioneer calls out his number and James tells him precisely how much he got the car for.
In "Private Channel", Mr. Williams, who plans to blow up the plane, is overcome with remorse when he hears the passengers' thoughts through Keith Barnes' Walkman. One passenger's thoughts about his young daughter Jenny strike a chord with him as he was motivated by the death of his own wife and daughter, who was much the same age as Jenny.
In "The Wall", Major Alex McAndrews returns to Earth through the Gate as he feels duty bound to report what he has discovered on the Paradise Planet. After he reports that the planet is an agrarian society without weapons of any kind, the US government begins to draw up plans to conquer it and use it as a staging ground to launch surprise attacks on its enemies. Alex comes to deeply regret his decision. Believing that he is about to introduce a snake to the Garden of Eden, he sabotages the scientific equipment which is maintaining the Gate and goes through it just before it collapses.
In The Walking Dead, after Daryl punches Negan for taunting Rosita about Abraham's death, Negan responds by brutally murdering Glenn. The look on Daryl's face is one of pure horror, as he slowly realizes what his actions have caused.
War of the Worlds (2019): Catherine is horrified to realize that the aliens learned about Earth because of a signal she helped in sending out when they sent a song included in it back down.
In Season 2, William shoots his daughter Emily as he believed she was just a host being used by Ford. The reason is because Emily mentions a profile card and William gloats "you went too far, I never told anyone about the card". But as he looks at the body, William sees the card in Emily's hand and realizes he killed his own daughter.
In the same episode, Dolores forcibly reprograms Teddy into a ruthless killing machine because she believes he's not going to survive outside of Westworld. But when Teddy slowly gains self-consciousness, he's very heartbroken that Dolores turned him into a monster and because his cornerstone is to protect her, he can't bring himself to protect her from herself. So, he makes one conscious decision which is kill himself. Afterwards, Dolores drops to her knees and cries after realizing her actions led to this.
The Wheel of Time: Perrin screams in agony after he kills his wife Laila accidentally. He is understandably in shock for much of the early episodes.
Bertram's former priest realizes with horror that when he told Bertram as a child that euthanizing his mother could be forgiven, then it was taken to mean (involuntary) euthanasia of other people was also okay, and he's killed 26 people since.
Rita is intensely regretful when she realizes her selfishness and cruelty has left her alone and friendless, and even isolated her one true friend, Isabel. When Scooter takes pity on her and brings her some clothes and money, she expresses particular remorse for not having treated him better.
The Wilds: After kissing her, Becca tells her parents about it and Shelby freaks out, afraid of her dad's reaction. She rejects Becca, later learning Becca's killed herself before her pageant performance, and is horrified.
Y: The Last Man (2021): Hero is distraught and then shell-shocked after she accidentally kills Mike, her lover, during an argument.