Dr. Fuji: "We dreamed of creating the world's strongest Pokemon... and we succeeded..."
In Brave the Wave, after getting scolded for pushing his Treecko too hard and got upset with his friends, Ash realized how bad he lost it as he sees that his friends were right about pushing his Pokémon too hard and apologized to them for his behavior.
In Cruisin for a Losin, after May loses her contest and is scolded for her behavior, she realizes how hard she pushed her Bulbasaur and sincerely apologizes to her for it.
In Take This House and Shuppet, May has a guilty look on her face when she realizes that she's really hurt Max's feelings during her argument with him and said some things that she shouldn't have.
In Pokémon the Movie: Black/White, Damon realizes his mistake and falls into despair when both Reshiram and Zekrom, regardless of whether it was the Black version or the White version, show him that his decision to move the Sword of the Vale resulted in the dragon force going out of control. This shortly leads the misguided antagonist to pull off a HeelFace Turn.
In Seeing the Forest for the Trees!, after losing his Gym Battle for his last Kalos Badge and went to the Winding Woods alone in order to contemplate things, Ash was visited by a concern Serena as she tries to cheer him up, but he gets upset with her instead. Serena lets what Ash said get to her and loses her temper, even throwing snowballs at him. However, they both ended up regretting their behavior and reconciled at the end of the episode.
In A Towering Takeover!, Alain has a guilty look on his face when he's forced to let Team Flare take Ash and his Pokémon captive. Alain also realizes that his attempts to protect the ones he cares about, especially Mairin and Chespie, and his joining forces with Team Flare, have potentially doomed the entire world. In the following episode, after Lysandre tells him that he used his battles with Trainers that can Mega Evolve their Pokémon as energy for his machine in order to control Zygarde, Alain is on his knees in shame and keeps punching the ground. However, Alain's able to snap out of his depression with Ash's help, and the Kalos League finalists team up against Lysandre.
In Trials and Determinations!, Ash's Rockruff has been in an evolution induced aggression and kept growling at everyone, even its friends. However, during Ash's Grand Trial with Olivia, Rockruff immediately comes to its senses when it realizes that it just attacked and knocked out its teammate, Rowlet. The next episode has another one when it bites Ash in its aggression, running away in shame afterward.
In Mission: Total Recall!, Lusamine had this reaction when Gladion told her off for her actions, making her realize how far she let her work and wanting to see an Ultra Beast got in the way of her family.
In Goodbye, Friend!, Goh decided to leave his Raboot in Hoenn as he believed it would be much happier their than with him. However, after being questioned by Ash on if he actually went and discussed this with the Rabbit Pokémon, Goh realized that he made a hasty decision and doesn't want Raboot to leave. By the time Goh realizes, however, it was too late and the train they were on speeds off. Luckily for Goh, Raboot had boarded the train in time and the two of them are able to fully reconcile.
In There's a New Kid in Town!, Chloe as a young girl got angry at her family Yamper for stealing everyone's attention so she wished for him to go away. However, Chloe soon realized her mistake and went out to find Yamper but was menaced by three Venonat in a dark playground and burst into tears as they approached but the Puppy Pokémon came out then shooed them away.
In Betrayed, Bothered and Beleaguered!, Ash is implied to have experienced this off-screen when Chloe told him how his Pikachu was feeling lonely and neglected in favor of Riolu. After deducing where his partner and best friend would most likely be going, Ash rushed to Pallet Town in order to fix things with Pikachu. Meanwhile, after saving Mimey from a Spearow and remembered how he first became best friends with Ash, Pikachu felt remorseful for running away and for thinking his Trainer didn't care about him anymore.
In Time After Time, Goh kicked himself for holding a grudge against his friend Horace for two years and snubbing him on the day they were supposed to meet up to hunt for Celebi, after finding a note that explains that the latter had fallen ill and couldn't make it.
In the manga Pokémon Adventures, Ruby does this when he realizes he was a huge Jerkass to his Feebas after she loses a Contest and caused her to run away. He only partly realized that on his own at best, and it takes a tongue-lashing from Wallace before it finally gets through to him completely.
In Assassination Classroom Terasaka is utterly horrified after seeing that he unknowingly put his classmates in jeopardy. The anger that drove him to work with Itona and his handler instantly evaporates and he briefly goes into denial, only to be slapped out of it by Karma.
Jean is horrified by his own actions, after successfully leading the other trainees to safety. Not only did people die on his command trying to reach headquarters, but he intentionally used the deaths of other comrades to pull the whole thing off.
Titan agent Annie is so horrified by the aftermath of the attack on Trost that she can only stand there in shock, apologizing to what might have been her friend's corpse.
In stark contrast to the previous two, Bertolt, the third Titan agent, initially shows no remorse for his actions. Even being reminded by Eren that he is directly responsible for Eren's mother's death (a piece of the Wall he kicked crushed her legs so she couldn't escape the Titans) garners no emotional reaction from him beyond admitted pity. Later, when confronted by the rest of his former squadron comrades, he breaks down and admits he hates what he's done and did come to care for his friends.
Both Levi and Hange experience a brief moment of this when they find out Titans are actually transformed humans.
Gyoubu Kasumi from Basilisk, after Tenzen grabs a flautist boy and throws him into the middle of their fight, causing Gyoubu to accidentally kill the boy's father when the old man tries to save his son.
Berserk: Guts, when he kills Adonis, a young child, after Adonis saw him murder Lord Julius.
Griffith, when Ubik shows him all the people who died, either by Griffith's own hands or due to his machinations, in his quest to obtain the castle he dreamed of. Unfortunately, this doesn't last, and Griffith goes from apologizing profusely and begging for forgiveness to the realization that he's too far gone to feel regret or remorse for his sins, and resolves instead to kick it into overdrive.
Later, Guts nearly raped Casca and bit her in the process. From that point on, he began to keep his distance from her while she kept hers.
In Black Lagoon, Roberta reacts like this twice. First after she seduces and brutally murders a mercenary, not realizing that Garcia (a preteen) was listening the whole time. She's so horrified that she freaks out and convinces herself that he's a hallucination. The second time, she blasts GARCIA of all people, in an instinctive trigger-pull near the end of El Baile de la Muerte.
Bleach: Hitsugaya has this when he and the others attack Aizen and believe that they succeeded, only for the illusion to drop and reveal that Hitsugaya has quite literally stabbed Hinamori in the back.
Kira has this reaction after he learns the truth about Aizen's plot, including that his friend Hinamori is in critical condition. He presumably was merely following Ichimaru's orders, and noted that he promised that Hinamori wouldn't get hurt.
Urahara in the "Turn Back The Pendulum Arc" when he realizes that he sent Hiyori into a dangerous situation all alone.
Don Kanonji when he learns that he had been turning ghosts into Hollows when he thought his exorcism technique had been sending them to Heaven.
And Ichigo when he finds that he stabbed Uryu while possessed by a Hollow. Of course, this is cut short when he finds that Ulquiorra is dying as well.
Van Argeno from Blood+ when he witnesses the results of his research turn members of the public into Chiropterans.
In the novel, Last Order claims that Accelerator never liked the killing of 10,000 sisters experiment in the first place and the reason why he acts so cruel to them is to discourage the remaining sisters from going after him.
A Certain Scientific Railgun. Kiyama Harumi has this, after the subjects of one of the experiments she participated in (children in her school class) fell into comas and the head scientist of this program put a gag order in effect and was more concerned about the data than about the children. Later, she found out that the experiment was deliberately dangerous.
Can also apply to Ian when Jeremy finds the pictures Greg took of him after whipping/raping him that Ian kept. Jeremy, as expected, reacts negatively and has a Freak Out, which leads to Ian's My God, What Have I Done?.]
The manga version of Chrono Crusade has Chrono do this after his Unstoppable Rage in volume 5. He's so distraught he can't even quite get out the words: "Oh, no. Have I done? Ro...sette!"
Lelouch has a Delayed Reaction version of this when the memory of his murder of his half-brother Clovis from the previous episode causes him to vomit (you see the bathroom sink water running indicating he did get sick).
Suzaku also has one of these when he realizes he's Jumping Off the Slippery Slope by trying to drug Kallen to get information out of her. Followed by Nina Einstein, once she witnesses the horrendous results of her FLEJIYA nuke.
Lelouch actually has another one of these, when he loses control of Geass and Euphemia gets hit with his off the cuff command to KILL ALL JAPANESE PEOPLE! The look of utter shock on his face spoke volumes.
Earlier in the series, he gets a similar expression upon being informed that his love interest's father was among the casualties of his latest battle. Although this isn't as objectively big as the aforementioned incident, it shook Lelouch rather badly and forced him to personally face the consequences of his actions and orders.
Darlton gets one of these after his hypnosis wears off and he realizes he just saved Zero by shooting Cornelia in the back.
Momo is horrified to learn Yuko is an Ill Girl who's not even supposed to run, let alone go through the heavy training Momo subjects her to. Yuko assures her she's a lot stronger after becoming a demon, though Momo's still bothered by it.
In Chapter 45-48, a pop star is killed by his own beautiful manager, because he asked her to stay by his side and work for him, only for him to constantly verbally abuse her. As she was in love with him and felt insecure because of her perceived ugliness, she went through plastic surgery before accepting the job. However, the man loved her natural self, and since he couldn't be honest with his feelings (which he could only express through the latest song he was going to produce), she eventually misunderstood his feelings and began to hate him. One of her friends points out that the singer still loved her and reveals so through a postcard with a song on the back dedicated to her. The woman breaks down at once she realizes her own foolish action.
In Chapter 197-199, a woman kills her younger sister, thinking that she stole her boyfriend. However, the boyfriend actually fell in love with the younger sister and wanted to break up with his girlfriend. The younger sister wanted to protect her elder sister's pride, so she only accepted the proposal if they lied about who approached who.
In Chapter 322-324, a singer attacks her former co-member out of jealousy for being engaged with the man she loves. However, the victim just wanted to make a different man, the one she actually loves, jealous, and it was a ploy. Even before learning the truth, the perpetrator regrets attacking one of her best friends, which leads to a suicide attempt that Conan barely prevented. The victim also quickly forgives her friend and does not tell the police the truth.
In Chapter 361-365, a man kills a group of bandits who broke into the house of his employer and killed his fiancée. The one murder he regrets is the one of the woman who turns out to be the stepdaughter of his employer, whom he helped raise. He began to understand why she faked a kidnapping and then broke into her own house, but only recognized her and understood her motives after she apologized to him right before he killed her. The fact that after he killed her, he treated her body with respect, shows that he probably wouldn't have killed her if he had recognized her earlier. He eventually realizes that his employer must have understood why the robbery happened and asked his butler to blame him, if he wanted to blame someone. The prized painting that the bandits were looking for, due to oxidation, at the end looks like it's crying in response.
Digimon Fusion: Much like Ken, Ewan Amano didn't realize Digimon were living creatures until his battle with Mikey. He also makes a HeelFace Turn, though it takes until the sequel for him to earn his partner back.
Yamaki actually yells this under the dramatic and appropriately messed-up sky created by his program Juggernaut, an attempt to purge digital life from reality that instead results in a massive and highly dangerous breach between the worlds. Of course, this a fellow about whom the line, "Looks like your pal Yamaki ripped open the sky again," has been uttered. This of course leads to him being fired, and after a good sulk, he begins his HeelFace Turn.
Beelzemon spends a good deal of time wandering the Digital World listlessly, thinking back over his actions after he kills Leomon and is later saved by Leomon's Tamer, Jeri. He's so disgusted by himself that he completely loses the will to fight and even to live, not even trying to fight back while a group of Chrysalismon beat him halfway to death. He (somewhat) snaps out of it when he finds out that Renamon and Rika risked their lives to find him, and, well...I think you knowwhere this is going.
Takato says this word for word after his anger at Leomon's death gives normally innocent and friendly Guilmon a Superpowered Evil Side in Megidramon.
Takuya's first use of his Beast Form results in him mindlessly trying to destroy everything in sight, including his terrified teammates. He eventually snaps out of it but still came within an inch of killing his surrogate little brother Tomoki and is promptly so frightened by this new power that it takes a full episode and Tomoki getting kidnapped for him to try using the Beast Form again.
Even while Brainwashed and Crazy, Kouichi is still able to have this reaction when he nearly kills Kouji. This is strictly because of Takuya, who is having a bout of it himself since Kouji only got hurt because he was Taking the Bullet for Takuya, screaming Kouji's name and unfortunately it's not strong enough to snap him out of the brainwashing.
Doraemon: Occurs in "Soap Bubbles". The characters cry and say this for minor offenses like smoking or bumping into people.
Vegeta had this twice, once when he allowed Perfect Cell to reach his perfect form and again when he allowed Majin Buu to resurrect.
Gohan had this too, thanks to his cockiness.
Vegeta after Future Trunks gets murdered by Cell. He realizes he's neglected his own son and goes on a Roaring Rampage of Revenge.
A short while before the above example, Goku had one of these moments on his own when Piccolo reminded him that Gohan was partially human, didn't share Goku's lust for battle, and thus didn't find any pleasure at all in getting curbstomped by Cell while his father simply looked on from a distance.
Goku also has a short moment of this after (seemingly) killing Frieza on Namek.
In the Buu saga, Piccolo tells Super Buu to kill the people of Earth, hoping that it will stall him and intending to wish back everyone with the Dragon Balls later. However, Buu then fires the Human Extinction Attack and kills everyone in the world in less than three minutes, leading Piccolo to have this moment.
Renton from Eureka Seven does this after he goes berserk and tears an army of enemy LFO's to shreds. He doesn't really have enough time to ask of God what he has done. He, instead, loses his lunch over the debacle.
The impact of this cannot be fully felt if you don't realize that up until this moment Renton (and many members of the audience) didn't realize that the entire time he's been fighting enemy LFO's, he's been killing people. He simply thought that enemy LFO's were robots.
Before this, Renton has a minor one when, after they have an argument, Eureka pilots the Nirvash in his place and gets critically injured. It's bad enough when he sees her covered in tubes and bandages in a hospital bed, then Holland rubs it in further, causing Renton to spend the next little while bashing his head against the wall outside the sickbay.
Happens to Caster in Fate/Zero when he sees the light from Saber's Excalibur. It reminds him of the joy he felt when he was with his beloved Jeanne and the latter's purity, and he manages to muster out "What... have... I..." before being killed.
In Food Wars!In Chapter 151 after Soma casually confesses to Erina's father and unknowingly to Erina and the rest of his dorm, of Jouichirou Yukihira being his father, Erina has a major freak out when she remembers all the times she has unknowingly insulted, her idol, his son, the cooking style, roots and the restaurant of said idol.
Doctor Marcoh from Fullmetal Alchemist. Now that he's gone and made the damn Philosopher's Stone already, he feels horrible about it. With good reason. Also, most of the protagonists in the Ishval arc. War suddenly doesn't seem so great anymore.
Edward Elric, in an attempt to bring his mother back to life, ends up losing his arm and leg and nearly bleeds to death, his brother's body is completely destroyed and he ends up as a soul in a suit of armor, and then he realizes all he managed to do was create a writhing mass of nightmare fuel instead of his mother. He really could have used some therapy.
For Edward, Al, and Izumi the greatest horror after their failed human transmutations was the thought that they had brought their loved one back only for them to die in agony again. The discovery that the humans they transmuted were soulless and not even similar to the loved one frees them from lingering guilt.
From the same continuity, Roy after killing Winry's parents.
Also, although being less emotional about it than the previous example, Roy after killing Bradley/Pride.
Mayo Sakaki in the 3rd Fushigi Yuugi OVA. When she realizes that her behavior is destroying the universe (and herself), and that love and obsession aren't the same after talking with Houki, she is Driven to Suicide and attempts to drown herself, believing herself to be beyond redemption.
In High School D×D, Lord Zeoticus Gremory has a moment upon realizing that he was forcing his beliefs onto his daughter Rias, such as organizing an Arranged Marriage to Riser Phenex as opposed to letting Rias choose a husband for herself when Riser was really a major jerkass and Rias is against the marriage proposal. Zeoticus's son Sirzechs helps Rias's Love Interest Issei Hyoudou defeat Riser in an Engagement Challenge; Zeoticus apologizes to Lord Phenex for her cancelling the engagement and he is Easily Forgiven. It's even lampshaded by Zeoticus's wife Venelana in Volume 5.
Kill la Kill: Ryuko has this when she ends up stabbing Mako while being controlled by Ragyo. The shock of it is enough to undo the brainwashing.
In HappinessCharge Pretty Cure!, Iona Hikawa/Cure Fortune spent half of the series giving Hime Shirayuki/Cure Princess hell over her Dark Secret, opening the Axia Box and letting the Phantom Empire free. Because of it, Iona's sister, Maria/Cure Tender, was defeated and captured by Phantom. When Iona finally confronts and battles Phantom, Phantom easily overpowers her and destroys her PreCards before revealing the truth - Maria's defeat and capture wasn't Hime's fault, it was Iona's: she wandered into the fight between Maria and Phantom and when Phantom targeted Iona, Maria took the hit meant for her. Iona doesn't take it too well. She gets another one when Hime finally gives her her reasoning for what she did - she was tricked into opening it after hearing a sad voice from inside.
In Hellsing, Seras wakes up from her berserk mode and is horrified of killing the ghouled soldiers of Hellsing, Walter also had this moment in the anime when he found out he nearly choked Seras with his wires after being hypnotize by a vampire.
In Higurashi: When They Cry, several of the characters have these moments. Heck, Keichi has two regarding the same horrific event.
Shion even wets herself upon hers.
That may be a very, very different kind of wet for all we know.
In the final episode of I'm Gonna Be an Angel!, after Silky sets their wings on fire, Mikael snaps out of his madness and when Raphael appears before him and confronts him with what his actions have led to, Mikael breaks into tears, expresses his remorse over what he has done and pleads his teacher to rescue everyone. When Raphael disappears, Mikael just resigns to the worst.
In JoJo's Bizarre Adventure Part 2, Strohiem has this reaction once the "Ultimate Life Form" (Satanna) escapes from what he thought was an inescapable cell, and proceeds to start slaughtering every single Nazi in the base.
Robin Mask suffers from this when he thinks he's killed Kinnikuman during their fight in the 20th Choujin Olympics. Especially noteworthy in that Robin was previously in an Unstoppable Rage- once it wears off, he realizes that he was taking the fight to seriously. While he's lamenting, Kinnikuman puts him in a finishing hold, winning the match.
Hiyori suffers this after she arranges for thugs to beat up Manabe for choosing Haruka over her. The encounter doesn't go as planned, ending up with Manabe getting injured - stabbed in the manga and sorely beaten in the anime - and sent to the hospital. She then suffers Heel Realization about how much of a Jerkass she's been.
For the same incident, Haruka also believes she's the cause of all the strife between Manabe and Hiyori for the latter's jealousy.
Guld Bowman In Macross Plus gets a simultaneous double helping of this, when he finally overcomes his Trauma-Induced Amnesia in the middle of a Macross Missile Massacre which he believes has killed Isamu Dyson, the person who he had blamed for the trauma. Actually caused by his own attempted rape of Myung, a memory he had suppressed until that moment.
Magical Project S Misao Amano (as her evilMagical Girl alter ego Pixy Misa) was destroying the city and almost killed her only friend Sammy and her parents, to the point where she ran away due to guilt, this was justified although it was her other personality did this and was unaware of what she did. The twist here was that what she did was really her (her repressed aspects,) and not brainwashing.
In the second volume, when Taishou realizes that he allowed his jealousy of Fukami working on a project with his best friend Buchi, he lets his anger get the better of him and he ends up raping Buchi. After coming to from a punch from Fukami, Taishou realized what he has done and he breaks down crying.
In the fifth volume, Fukami ends up raping Buchi because he developed feelings for him and he was going to admit his feelings for him, but his mother abandons him which causes him to become lonely and he feels that Buchi wants to be raped like back when Taishou raped him. But on the morning after he rapes Buchi, he to immediately regrets what he had done when he sees Buchi.
In the movie version of Magical Girl Lyrical Nanoha, Precia gets one over how she had treated Fate when she remembered that Alicia had always wanted a little sister. Unfortunately, by the time she remembers this, it's too late to apologize or make amends.
In episode 7 of StrikerS, Teana's recklessness almost ends up getting her best friend Subaru hit by friendly fire (fortunately, Vita was able to intercept it with Graf Eisen). The entire time that Vita's scolding her she's paralyzed with guilt, and at the end of the episode she breaks down into tears. Even worse, she ended up making the same mistake the next episode during the "White Devil Incident", causing her to have this reaction again in episode 9.
Subverted in ViVid Strike!. Rinne was initially horrified when she sent three girls who had been viciously bullying her to the hospital. Then she found out that the girls lied to their families and claimed she attacked them unprovoked, at which point any guilt she felt disappeared. Double Subverted in the end when it turns out that she never actually stopped feeling guilty (her cold personality being a poor attempt to cope). It's not until Fuuka defeats her that she's finally able to forgive herself.
Bisco Hatori's Millennium Snow has the vampire male protagonist, do this after he grazes Chiyuiki's neck with his fangs, meaning she will have to live for a thousand years with him also counts as a What the Hell, Hero? moment, as Satsuki promptly tries to kick his ass afterward.
In Mobile Suit Gundam Wing, Heero is overcome with this after destroying an airplane carrying what he believed to be senior members of the OZ organization. Then Wufei arrives and tells them that he just actually killed all of the senior leaders of the United Earth Sphere Alliance who wanted to make peace with the space colonies. It was then everyone realizes they'd just been suckered into Magnificent Bastard Treize's Batman Gambit; it was also then when they realized this was not a black-and-white war.
In his backstory, shown in Endless Waltz he had another: during a mission he set up explosives to blow up a military base. A miscalculation on his part led to a Mobile Suit exploding near a residential area, killing lots of innocent people including a little girl he'd befriended the day before and her dog.
In Mobile Suit Gundam SEED, both Kira and Athrun go through this simultaneously following the Battle of the Marshall Islands, where they kill each other's friends and then attempt to kill one another. Athrun gets it worse because he believed that he succeeded. Both have to be snapped out of it by the people whose care they've fallen into, though in different ways.
An offscreen example happens between SEED and its sequel. In the first series, Yzak Joule shoots down a fleeing civilian shuttle he believed to be carrying retreating soldiers (still viscous, but not to the same degree). He finds out after the war, and was stated to have been horrified. He was put on trial and sentenced to execution, but pardoned by the new administration as part of a mass amnesty. Come the sequel, he acknowledges to Athrun that he deserved death.
Saji Crossroad in Mobile Suit Gundam 00after realizing that his cowardice began a chain of events that resulted in a group of resistance fighters and helpless refugees being massacred at the hands of the ruthless A-LAWS.
In Monster, after seeing all of the death and despair caused by Johan Liebert, Franz Bonaparta breaks down completely, feeling guilt for being the man who made Johan into the monster that he is.
Musuko ga Kawaikute Shikataganai Mazoku no Hahaoya: Demon idol Valentine's introductory arc features a side plot in which demons are demonifying at random in populated areas. The only commonalities are the demons themselves didn't seem to do it on purpose and have no memory of the fact afterward, and each incident featured Valentine's music playing somewhere. This makes Zeke suspect that Valentine has the power to force demons into their demonified forms against their will, and suspects she's doing it intentionally. He's half-right, in that Valentine's voice can force demonification, but Valentine herself didn't know she could do that. For this reason, when her first concert results in the demons in the audience starting to demonify, she's just as shocked as everyone else. Events work out so that everyone is made to think it's All Part of the Show, but Valentine is horrified to discover what she can do, as her own voice could destroy her dream peace between humans and demons. She approaches Merii, fully prepared to have her vocal cords completely removed by Merii's healing powers. Fortunately Merii is able to solve the problem while still enabling Valentine to continue singing as an idol.
Mikoto breaks down when she realizes she was responsible for killing her best friend Mai's brother Takumi... and her own grandfather.
Shizuru also gets a slightly more understated one after her resurrection in the Grand Finale, crying openly over the fact she'd forced her lesbian crush into a Taking You with Me situation because she'd gone out of control. Not as severe as some, but given Shizuru's graceful serenity over the entire series to that point, seeing her outright crying and apologizing through the tears had impact.
Yukino after she is blackmailed into trying to kill Mai. Even after the almost victim later thanks her for helping her find Takumi, she still feels quite guilty.
In My-Otome 0~S.ifr~, Elliot has this reaction after trying to kill Sifr on Una's orders, thus resulting in Lena being forced to block an attack, leaving her open to M9, and Lena is eventually defeated after overloading her gem. After seeing her in tears over it, her companions forgive her, although Sifr asks if everyone, having withheld information from her all along, wants her dead.
The title character of Nadia: The Secret of Blue Water has a look like this toward the end of Episode 20, after taking a bath with Electra where she learns that she had misunderstood Jean's friendship with Electra. Earlier, she had been quite nasty to Jean (in a fit of jealousy) when he attempted to compliment her (as advised by Electra). She later learns that Electra only considers Jean as a brother, and feels quite remorseful for her hair trigger outburst at him. (The same is true in that episode when she realizes, again from her talk with Electra, that she has misjudged Nemo and the Nautilus.)
The Fourth Kazekage's reaction to seeing Gaara as a sane, Wise Beyond His Years shinobi who is now Kazekage and the Commander of an entire army of ninja from across the globe, finally realizing how much of an idiot he's been. Ironically, this only happened after his death, via the Edo Tensei.
For a villainous example, in the 3rd film (Guardians of the Crescent Moon Kingdom) the baddy Ishidate accidentally turns his employer—and more importantly, paymaster—to stone. Oh, Crap!.
Sakura has this reaction when she realizes what the promise she got out of Naruto did to him.
Shinji Ikari has such a moment after his EVA nearly kills Toji Suzuhara due to his inability to fight. This haunts him to a greater degree in the manga since he actually kills Toji, and Kaji tells him to take accountability because he didn't try harder to save him, just standing by until his father activated the Dummy Plug
He has another that pushes him into a Heroic BSoD after he is forced to kill the angel Kaworu.
In the third Rebuild of Evangelion movie, Shinji has not one, but three such moments - First, when Kaworu shows him the devastation caused when he inadvertedly set off the apocalypse in a desperate attempt to save his teammate during the climax of the previous movie. Next, word-for-word, when he realizes that, on top of that, it was completely for naught since the girl in question is still dead and what he thought was her is just a clone of hers. The third time occurs when he sets out to atone for this and sets out to Set Right What Once Went Wrong. Except, the Reset Buttonis a lie, and all the supposed "Spears of Hope" will do is to blow the pathetic remainder of humanity to hell. As he sees the destruction begin around him, he reacts with utter mortification. Needless to say, by the time that movie is over, he's reduced to a near-catatonic shell, mad with grief and guilt.
In the Skypiea arc, more specifically Wyper's flashback: Calgara and his village begin acting coldly towards Noland after he cuts down a great many of their trees, which they believed their ancestors to be in. This is after Noland saved them from a plague and they threw a party on his behalf. When Calgara's daughter learns and passes on the knowledge that those trees were the source of the plague that had harmed them in the first place, just as Noland and his crew are leaving the island, the entire village has this reaction.
In the Fishman Island arc, Jimbei expressed guilt for letting his hatred for humans get the best of him when he indirectly let Arlong to go to East Blue and terrorize Nami's village for years. He felt quite ashamed of this and offered to accept any punishment Nami wanted to give him.
A comedic example in the Zou arc, Usopp upgrades Nami's Clima-Tact, but Nami gets a little carried away with it, invoking this from Usopp.
Nami: It's easy to hold and even easier to twirl! You're the best, Usopp! (Unleashes lightning bolts at nearby Minks)
Nearby Minks: WAAH! WATCH IT!
Usopp: What have I unleashed?
Oh, how shall we count the ways in which PandoraHearts does this to us?
First, Oz thinks he stabbed Gil early in the series and freaks out He lived. Then Oz undergoes one around the time he discovered he was actually B-rabbit and thus responsible for Alice killing herself to save him and also when he makes her disappear. The chapter title for 75 is called "Alone" for a reason.
Alice herself in Retrace 76 where she screams a big no upon seeing her sister die and say it's all her fault that everything happened. Then she decides to undo everything and wipe her memories.
Sayaka has this reaction when she makes Madoka cry after she yells at her for not using her latent power to fight witches. Unfortunately, this realization helps push her towards the Despair Event Horizon and she becomes a witch.
Not to mention Madoka herself had this reaction two episodes prior, after throwing Sayaka's Soul Gem off a bridge and onto a moving truck to keep her out of a fight only to find out that said Soul Gem literally contains Sayaka's soul, and by throwing it away she almost killed Sayaka.
Hardner from Rave Master has this when he finds out that Nagisa, the girl whom he tortured, is actually his daughter.
Retired Heroes: An adventurer retired from being a soldier when they found a group of demons masquerading as merchants, and slaughtered them all—including the children. He was so horrified that he resigned and started Walking the Earth. It gets worse when his partner (who is also a demon, though he didn't know at the time) points out that the demons weren't masquerading as merchants to spy on humans; they were merchants, who accepted the risk of being killed if they were discovered because it was still the safest way to make money.
In Say I Love You, Yamato starts to realize this when Aiko calls him out on the rumor that he was seen leaving Megumi's apartment. She tells him that Mei, his girlfriend, was deeply hurt by that rumor. He initially doesn't think there's anything wrong with it, since he states there's nothing going on between them, and he's simply going there for dinner. Aiko then asks him that if the situation were reversed, where Mei was going to another guy's house without his knowledge, if Yamato would be okay with that. He runs off and begins searching for Mei, canceling his photo shoot with Megumi in the process.
Keito Nichi in Star Driver when she realizes that by trying to manipulate and backstab Head, she has actually doomed Sugata to either death or eternity as Head's slave. She was trying to make it so he could rule the world out of her love for him.
Ellen in Suite Pretty Cure ♪ suffers this first hand as she watches a boy she had accidentally convinced to continue run away and his father be struck with a Negatone's wail, pushing them into despair. Bassdrum points out that she had done this so many times and, driven to despair herself, tosses away her Cure Module. However, Hummy's there to get her to realize that, deep down, she wants to make up for those times and helps restore her Heroic Resolve.
Sword Art Online: Asuna's father gets such a moment upon the reveal that Nobuyuki Sugou, for whom he had set up an Arranged Marriage with Asuna and genuinely believed to be a friendly, bright guy who he wanted to inherit RECT Inc., was in fact a major Bitch in Sheep's Clothing who not only conducted inhumane experiments on 300 SAO survivors, but also molested Asuna and tried to rape her right in front of her actual Love Interest Kirito; not only that, but when Sugou's crimes are made public, it causes a massive public scandal that not only causes the RECT Progress branch to collapse from lawsuits, but also impacts the main company itself. Asuna's father was so horrified at how badly he misjudged Sugou that he stepped down from his position as CEO of RECT, and Asuna herself just barely managed to convince him not to retire completely.
In the second Tenchi Muyo! movie, Ryoko's been incredibly suspicious of Mayuka, though the others are just blowing it off as Ryoko being jealous. Near the end of the movie's second act, Ryoko gets fed up and begins fighting with Mayuka and Tenchi gets between the two. Ryoko's begging Tenchi to listen before he lets his emotions get the better of him and slaps her. Tenchi's utterly shocked at what he's done, but is unable to apologize before Ryoko teleports away. It ends up being Ayeka who is able to get to Ryoko... just in time to prove that Ryoko's warnings were right.
Tony in Toward the Terra after he accidentally kills Matsuka, a fellow Mu, while attempting to assassinate the antagonist. Complete with enough angst to last the rest of the series.
Shown in Tsubasa -RESERVoir CHRoNiCLE-. While not actually said out loud, it is spoken perfectly clear by the look on C!Syaoran's face when he looks down at what's left of his loved one, C!Sakura, who he accidentally impaled.
Fai during the Infinity arc is forced to kill Sakura thanks to his first curse. He then proceeds to lose control of his magic, tear up the arena around him, and nearly commits suicide.
The protagonist from Tsukihime goes through this in every route, after he regains control/consciousness from whatever insanity/inversion/dream-turned-reality he just went through, all of which generally involve him causing bloodshed and death.
Windaria Izu/Alan when he realizes the magnitude of what he's done by flooding Itha/Lunaria and how many lives he destroyed.