Takashi Sugurono. Some consider that he was one of the sadistic teachers for the Team Summer A candidates to already push him really close to the MEH, but especially counted it when the Final Test rolled around. So when he was on-screen again during the Ryugu Shelter arc, he was already considered past the MEH so that his decision to kill part of the inhabitants, without their prior knowledge, in order to temporarily secure the continued survival for the rest of the inhabitants seemed like an unnecessary cherry on top. Other readers considered the Ryugu Shelter spoiler to be his actual MEH. Though Takashi does eventually redeem himself in some readers' eyes.
Ukai from the Team Summer A candidates crossed it when he decided that, in order to kill Ango, he would take advantage of Shigeru's naive, good-natured heart and made him lure Ango into a trap. And then decided to shoot Shigeru, because he wanted to help Ango. Fortunately, Ukai dies shortly after.
Sora Takeuchi from Air Gear proved himself an as asshole when he threatened to physically harm his ex-girlfriend Rika Noyamano —who is also pregnant with his own child.
Akame ga Kill! wakes up with one of these each week more or less, but special mention goes to Wild Hunt, particularly fat pedo-clown Champ, who murder and rape people on a bi-daily basis with the authority that comes with having Syura, the Prime Minister's son, for a leader. What really sends them over the line is they do it to Bols' (a loyal imperial soldier and with a decent personality) WIFE AND CHILD ON HIS GRAVE.
Tetsuo of AKIRA crossed one of these himself. Tired of having to be rescued by Kaneda and wanting independence, he felt ecstatic when he developed superpowers while in custody of the military. When Kaneda does arrive to rescue him, and military soldiers show up, he blows them away, hurting Kaneda in the process. Instead of showing any sympathy for him or sorrow for what happened to him whatsoever, he just laughed and said "Oh, that's right. I forgot you were there!" And boasted on how he won't need to be rescued anymore, even proceeding to attack Kaneda again... this time on purpose! Attacking your own friend with NO remorse!? That's just wrong. And that's even beforewhat he does to Yamagata.
A good example of a crossing of one of these that pushes you over the Despair Event Horizon is when thugs break into your house and murder your entire family, which is exactly what happens to Yurippe in a flashback in episode 2 of Angel Beats!.
Yuri herself almost crosses the line in the manga by killing all the students, starting with the first graders. The scary thing is, she would've done so then and there had Hinata not intervened before the first murder was supposed to take place.
It begins with one, as the Colossal Titan and the Armored Titan destroy Wall Maria. The massacre that follows is horrifying enough, but even a year later the situation for humanity is so grim that the government is forced to cull 150,000 refugees in a mission to reclaim lost territory to avoid mass starvation and civil war. In total, humanity lost 20% of their total population and 30% of their territory, much of it vital farm land needed to support the population. There is absolutely no doubt that the creatures responsible are pure evil. But then it is Subverted, when it is learned that Team Dad Reiner and Extreme Doormat Bertolt as well as Broken Bird Annie are the ones responsible for the entire thing and did it when they were kids. All three are fully aware of just how horrible their crimes are, absolutelycrushedby guiltand deeply traumatized over having to do it. It instead serves to make them Tragic Villains, having already committed an unforgivable act before they were old enough to fully grasp their actions and learn to care about those they were sent to slaughter.
The Beast Titan crosses it in its first appearance when it interrogates a Survey Corps Member and has him devoured by a bunch of Titans as an afterthought. Unlike the above examples The Beast Titan cracks a joke at his victim's expense. It's no wonder the Beast Titan has a 'Cruelty' ranking in the guidebook.
The Survey Corps cross it hard during their invasion of Marley, as they kill many innocent Eldians and Marleyans including those totally unrelated to the conflict, including young children. It becomes so bad that Jean actually wanted to defect right on the spot.
Now Eren himself has crossed the line by unleashing every one of the Wall Titans to kill every human outside of Paradis Island, an event known as the Rumbling.
As a Dark Fantasy series, Berserk has many villains that perform really sickening acts. In terms of crossing the Horizon, several characters stand out.
The most notable example of this occurs during the Eclipse after Griffith crosses the Despair Event Horizon near the end of the Golden Age arc (which is about the point where the anime ends as well) and activates his Crimson Behelit. Griffith, Guts and everyone in the Band of the Hawk gets transported to the Nexus, a place that to mortal eyes looks downright Hellish, where the Godhand and every demon in the Berserk universe has gathered. Griffith, distraught over the destruction of his dream and wanting more than anything to have a second chance, does a truly malignant FaceHeel Turn, choosing to sacrifice the entire Band of the Hawk and betraying everyone he has ever led in order to become the fifth member of the Godhand, Femto. And as if all this wasn't bad enough, Griffith then goes the extra mile across the Horizon with his very first act upon being incarnated as Femto, which is to brutally rape Cascato insanityright in front of Guts, who is being pinned down mere feet away from the act after he had just made the dire decision to chisel off his left arm in a last attempt to save her. And it's made even MORE heinous in that Femto is raping her in a way that is mirroring Guts' childhood rape experience. This is the epitome of Moral Event Horizons in all of fiction. After this, Griffith acting like a hero when he is reincarnated on Earth tends to be just a little bit ironic.
Particularly because the vessel that Griffith used for his reincarnation on Earth was Guts and Casca's child, which was conceived just before the Eclipse, but which was corrupted by what Griffith did to Casca as Femto. A kid that, had all of this not happened, would possibly have been Griffith's godson. Yeah.
Gambino, Guts's gruff mentor/father figure, loses all our sympathy after he sells Guts, who was just eight years old at the time, to a pedophile soldier named Donovan for three silver coins, resulting in a traumatic rape that still affects Guts even after he is all grown up. Particularly when we learn Gambino's reason for it immediately before Guts kills him in self-defense — he called Guts "disgusting" and felt that he "can't be raised to be loyal like a dog," since Gambino blamed the kid for the death of his lover Shisu from the plague.
The King of Midland, who after ordering Griffith thrown in the dungeons and put to the torture for having sex with his daughter Princess Charlotte, tries to force himself on her out of madness. Charlotte just barely manages to fight him off, and the experience alienates her from her father, to the point where she won't even acknowledge him on his deathbed.
Inquisitor "Bloody Scripture" Mozgus is just as horrible as you'd expect a fanatical religious nutjob with too much power and not a shred of objectivity can get. While it's pretty obvious from the start that he's Bad News, when a band of starving refugees attempts to steal some of the ample foodstuffs sent to Mozgus and his retinue, he spots among them a woman with a starving infant. When she begs him to feed her child, he gently takes her along to his residence, lauding her courage and dedication. He sends away the child to be fed and cared for, then escorts her to a room while extolling the fact that while her intentions were good, she still has to expiate her sins. Then he opens the door, where we see the other refugees being horribly tortured, and the poor woman is dragged, stripped, and tied to another torture device over her increasingly frantic pleas... then the door closes. It's as nightmarish as it sounds, if not more so.
As bad as those are the worst has to be Emperor Ganishka. If you name it he has done it: ethnic cleansing, putting POWs on the front lines, widespread torture, attempted rape (of Charlotte, again) to more horrifying examples like turning the Midland capital into a city of death, using black magic to conjure evil spirits to fight for him, forcing pregnant women into pits of chained apostles to produce demon soldiers who tear their way out of their still living mothers, and using artificial methods to becoming an even more powerful demon that would destroy everything. All the while bragging about making the world into hell. This guy was so evil that when Griffith/Femto faced off with him following his reincarnation, the fans rooted for Griffith/Femto.
Sosuke Aizen has had many candidates for these. What's arguably the worst of them all? Using his powers to fool Hitsugaya into thinking he's stabbing him...when in reality, the one he's stabbing is Momo Hinamori, Aizen's own ex-lieutenant, as well as the person Hitsugaya has sworn to protect. Hitsugaya's horrified screams as the illusion breaks and sees what he has doneto Momo are EPIC. So monstrous. So cruel. Guess he'll still have his leather pants on, though. Once he becomes a deity, he decides to butcher Ichigo's home town by having his aura eradicate anyone near him, killed Gin in a brutal matter and planned to hang Tatsuki just to see Ichigo's reaction.
Many readers consider Mayuri Kurotsuchi to have crossed the horizon when he experimented/tortured Ishida's grandfather to death along with over 2000 other Quincy, and then showed Ishida a photo of his grandfather's corpse. There's also the time where he turned three subordinates of his into bombs without their knowledge.
Mayuri Kurotsuchi's equallyEvil Counterpart, Szayelaporro Granz. Not only does he take delight in torturing Renji and the aforementioned Ishida slowly and painfully, but when Kurotsuchi and his lieutenant Nemu arrive to face him, just as Kurotsuchi is about to defeat him he grabs a captured Nemu, rapes her with tentacles to forcibly impregnate her, and kills the poor girl (one of the biggest Woobies on the whole Bleach, natch) after emerging from her body, leaving an empty husk. This is so squicky and cruel that a good part of the fandom saw the Fate Worse than Death that Kurotsuchi dealt to himas something to cheer for.
Nnoitra does this when he hints he intends to rape Orihime at some point (he stuck his fingers deep in her mouth in the manga for crying out loud — for those who don't know, sticking one's fingers in someone's mouth during sex is a very standard kink in Japanese porn, and it had to be bowdlerized in the anime), and in the backstory, his hatred towards Nel led him to collaborate with Szayel so he could take away her powers because he was jealous of her for being stronger than him and then he kicks her out of Hueco Mundo. He immobilized Orihime in the very creepy manner described above and forced her to watch as he has his subordinate Tesla beat Ichigo to death. Thanks to a Big Damn Heroes moment by Kenpachi, however, Ichigo is safe and Orihime heals him.
We also have Tsukishima and Ginjo conspiring to cross the MEH with each other's help. The first brainwashes almost everyone Ichigo cares for to turn them against him and break him in body, mind and soul, and the other sets up a Memory Gambit that involves erasing his own memories of being an enemy, to get close to Ichigo and train him up until it's the moment to break him.Horrible and brilliant at the same time.
Subverted in the case of Yukio. He gleefully claimed to have crossed this via driving his parents to suicide, but Hitsugaya quickly deduces (and shows!) that he wasn't as heartfelt and happy about it as he believed, driving Yukio to defend his parents and to a Villainous Breakdown.
The Big Bad of the final arc, Yhwach, crossed it in his backstory. In order to augment his own power, Yhwach power-drained and thus killed off the "Gemischt" Quincies (those who had partial human ancestry) and the "Echt" Quincies (full Quincy ancestry) regarded as "impure". Let us be clear on how far past the event horizon Yhwach has gone, ALL of those killed were his descendants. And that included Ichigo and Uryuu's respective mothers, and should have included Uryuu (he only survived due to a mysterious special power)...who was 8 years old at the time. So that's genocide, familicide, and attempted infanticide, all in one act. Oh, and did we mention that Uryuu's mother lingered in a coma for three months before finally succumbing?
Blood-C: Fumito Nanahara showed his true colors when he let the main cast (except Yuka) and the entire town to die in the hands of the Elder Bairns. But what really hits the marks is shooting Saya in the eye and taunting her to catch him as he leaves. And even before that, he's the one who brainwashed Saya in the first place.
Blood+: Diva crosses it when she rapes Saya's younger brother Riku so that she can bear his child, and then kills him.
Liang Qi from Canaan crosses this when she throws Hyakko through the Despair Event Horizon via tricking her into killing her savior and love Santana, and then mocking Hyakko's grief gleefully.
Hard to imagine a shojo anime like Candy Candy to be on the list but there's two in the series that are added on the list,
Eliza has several moments of dog kicking, but her worst actions are framing Candy and Terry to get Candy expelled from St. Paul School and scheming with Ruth to get Candy's reputation smeared because she took the amnesiac Albert into her household.
General Muoro and his lackeys showed their complete willingness to torture Sheeta to squeeze the secrets out of her and also tried to kill Pazu. Which also makes Muska's massacre of them a case of Kick the Son of a Bitch.
Code Geass is known for many morally ambigious characters (particularly with Lelouch) but there are those who stand out:
Schniezel crosses this when he leads Nina to believe that building FLEIJA would fulfill Euphemia's wishes, which directly leads to Nina's (arguable) crossing when she actually builds the damn thing! And before that, Nina nearly attempted to suicide-nuke the city to call out Zero for Euphemia's death. Yes, she's grieving, but planning to wipe out everyone, including your classmates, with nuclear annihilation is when you've just gone too far.
V.V. crossed it where he's the one who killed Marianne which sets the whole plot of Lelouch's rebellion in the first place all because of pure jealousy and even lied about it to his own brother, Charles, who later figured it out.
Vamdemon/Myotismon was the Digimon series's first ReallyBig Bad. If his string of Kick the Dog moments - he tortures and kills his Mooks, he captured Tailmon/Gatomon when she set out looking for her partner on her own and whipped her into a Child Soldier, he has his followers invade the entire city of Tokyo and kidnap its children to weed out the eighth Chosen One, and that's for starters - don't gradually nudge him over the Moral Event Horizon, then Wizardmon's child-scarring death - taking an attack meant to kill Gatomon and Kari, by the way - certainly does. It makes it downright beautiful when the fact that Vamdemon just made it extra personal to Tailmon and, by extension, Hikari triggers Tailmon's evolving into Angewomon and impaling him with an arrow. Even that doesn't stop him, however, and he gets even worse.
Piedmon has committed multiple Moral Event Horizon-worthy deeds. Genocide against the Digital Guardians, skewering poor Chumon, massacring Primary Village (which is filled with Digi-eggs of baby Digimon), turning the kids and their Digimon into keychains, and trying to outright murder the two youngest children by cutting the rope they were climbing are all things he did and took sadistic joy in doing.
While he wasn't as bad as Myotismon or Piedmon, Puppetmon crossed his MEH when he threatened to kill Yamato/Matt if Takeru/T.K. didn't come with him...and then tried to kill the kid with a freaking gun. And if that one's arguable, then killing one of his own underlings who was begging him to take him with him is definitely going beyond the pale.
Machinedramon's pretty vile too. His most likely MEH moment was killing the hoard of Numemon that were trying to protect Kari by blasting them all.
If you think that's bad, you haven't seen Digimon Savers. Kurata crosses the line when he specifically made a machine to destroy Digimon permanently and then used it. Upon realizing that he had made it worse, he made it even worse.
Kouki from the same series had no qualms about holding a city hostage, not caring about the thousands of lives lost. His comrade Nanami kills Digimon out of a desire to fill a lonely void in her heart, and his other comrade Ivan is doing it to get money for his family. Kouki? Does it For the Evulz.
MetalPhantomon also crossed it by using the DATS agents' worst fears and memories against them in order to suck out their life energy. Thomas got it particularly bad.
Even before she got captured by the Diclonius Research Facility, Lucy spends a good amount of time going to different peoples houses and murdering the families of those homes, just so she can have a place to eat and sleep for a couple of nights. The news even reports Lucy as a serial killer, which she was.
Although some interpretations feel that, while Kouta could never forgive Lucy, he could, and did, accept Nyuu by giving her a Mercy Kill.
Sabertooth's master Jiemma, kicks out Yukino for losing a match and that's after he threw a wine glass and ordered her to strip.As if that's not enough, he then later almost erases Lecter, simply because of the fact that a cat is wearing the Sabertooth mark.
Invel Yura of the Spriggan 12 crosses it when he forces Gray and Juvia to fight each other to the death, hoping that Gray, by killing a comrade will awaken his inner darkness and kill E.N.D. (who happens to be Gray's friend/rival Natsu), an action that forces Juvia to perform a Heroic Suicide, since she doesn't want to kill Gray or have him live with the guilt of killing her).
Freezing has Louis L. Bridgette, the leading female's half brother. Sure, it was sick that as a kid, he had a creepy fondness for touching Satella that led her to having severe issues, and everybody in the forums were clamoring for his castration. But now? His obsession with her has exploded to the point he rapes another woman just because she looks like Satella. Seriously, WTF.
Mark Spencer, the head of the Chevalier and overseer of the E-Pandora project. He deems the E-Pandoras as something that can be easily replaced and tortures Elizabeth simply because she tried to fight against this injustice.
The Big Bad, Akito Soma, has several options, but the closest to this is how she treated the kindly nurse Kana, by blaming her for Hatori's eye injury that she caused because she was angry that Hatori wanted to marry Kana and asked for permission to do so. The Mind Rape was so bad that Kana ultimately agreed with Akito's blame of her and fell into permanent grief/madness and had to have her memory wiped by Hatori.
In Akito's and some of the fans' opinions, Shigure crossed it when he slept with Akito's Evil Matriarch of a mother Ren, as a revenge for Akito sleeping with Kureno. His betrayal is somehow worse, considerin Akito's extremely troubled relationship with her abusive mother, which was the indirect reason why she even cheated on Shigure in the first place; she slept with Kureno to reassure herself that he wouldn't leave her, coming from Ren always telling her that everyone would leave her.
And all those abusive parents:
Ren Sohma crossed the MEH long before the story even took place by threatening to have an abortion if she wasn't allowed to raise her baby as a male. That baby? She'd become the above mentioned Akito, and being forcibly raised as a male would be her Start of Darkness. The worst about it? Ren's reasons: She was jealous of her unborn girl because her husband Akira was so happy about becoming a father. The ongoing rivalry (which only gets worse when Akira dies) is the main motivation behind Akito's aforementioned and constant puppy punting, eventually driving her to become the Manipulative Bitch that the fandom Love to Hate. Summed up, Ren's horribly selfish and cruel actions lead to almost all the crap that happens to the Sohmas in story.
Kyo's Father crossed the line when he told Kyo it was his fault his mother had committed suicide, especially because of his motivation: he felt guilty himself, since he verbally abused his already-unstable wife (who may not have shown her love of Kyo in the healthiest manner, but did love him as much as she could in her terrible mental state.
Rin's parents cross it when they physically and psychologically abuse her... and then abandoning Rin when she collapses out of stress and is delivered to a hospital, basically telling her (a nine-year-old!) to never come back.
Yuki's mother: When she practically sold Yuki to the already unstable Akito as a "playmate", fully knowing that Akito had completely snapped over Ren's abuse and become abusive herself. It's no wonder that her oldest son Ayame magnificently called her out later.
Momiji's mother crossed this when she told her son that giving birth to him was the most horrible thing that ever happened to her and that he made her sick. She even lets Hattori delete her memories of Momiji as a consequence. One could argue that she was already mentally ill to start with, but even when it might explain a little, it's still NOT an excuse.
It's hard to decide when Kyoko's parents did, but probably when they kicked her out when she returned home after a long stay in the hospital (due to the fact that she tried to end her own career as a gang member and got beaten up as a result), solely because it tarnished their reputation. It's so bad that her love interest and future husband Katsuya gives them one HELL of a "The Reason You Suck" Speech before he takes Kyoko in.
Gauron almost shooting Kaname's teacher in the face for calling him a coward.
Seina getting Kugayama to pilot the Behemoth by telling the kid, who thinks she's his sister, that she'll be nothing to her if he doesn't.
Fushigi Yuugi's Nakago crosses this when he manipulates Suboshi into crossing the MEV with him by killing Tamahome's entire family, most of whom were children barely the age of ten, in what Suboshi (himself NOT a saint) believes is an act of revenge for his very much alive twin brother Amiboshi. It hurts even more when you realize that Tamahome had arrived just in time for his favorite, youngest sibling Yuiren to die in his arms, and that the second child Chuuei had tried to protect his siblings.
Gankutsuou: Arguably, when the Count kills Franz by mistake while trying to kill Albert in a brutal and gory way in front of his mom. The fact that Albert and Franz are barely more than children doesn't help. Interestingly, this marks a significant difference with the novel, where Mercedes not only knows about his plan to fight Albert in a duel, but begs him and eventually convinces him to spare her son
Andrea trying to rape his own half-sister Eugenie, then seducing and bedding his own mother and finally poisoning his father. And then getting away with everything like a Karma Houdini should.
And Heloïse Villefort. She seems perfectly normal in her first few appearances, with a warm motherly appearance and pleasant smile. She is the stepmother of Valentine and is the second wife of the crown prosecutor Villefort. She is the biological mother of her young son Edward, from her first marriage; however, Valentine is to inherit all of the fortune, leaving her stepmother jealous because Edward doesnt get a single penny. So when the Count seduces her and innocently introduces her to toxicology and gives her a deadly ring which releases a deadly poison Heloïse becomes murderous and tries to poison Valentine and her husband, as well as inadvertently almost poisoning Albert and poisoning one of the servants of the Villefort household. And she does all this while maintaining her angelic motherly facade up till near the end of the series when her husband finds out what she's been doing and points out that she's nothing more than a murderous insane woman. She tries to deny his accusations before she breaks down and collapses to the ground, finally giving in to her insanity. Her husband then puts her in an insane asylum for the rest of her life. Plus the scene where she masturbated while thinking of the Count and the poison ring he gave her; in essence, she was also getting off to the thought of killing her stepdaughter and husband.
Keido may have crossed it at one of two points—either when he tried to prevent the Adam and Eve of the new world from being an incestuous couple by sacrificing hundreds of children in horrific experiments, or when he murdered his old friend Kurosu in cold blood for no other reason than seething jealousy.
Kurosu Ouma crossed it when he agreed to go ahead with the pregnancy that would kill his wife, so that his daughter could trigger the apocalypse by sexing her new brother up. About the best that can be said is that he wasn't too happy about it afterwards.
Averted by Pino in Gunslinger Girl. Right when he's about to kill Aurora for walking in on his plans one too many times, Flanca warns him to refrain from doing so. Played straight, however, by Ski Mask Guy in chapter 83 just for being the only one present besides Jose when Henrietta's bad memories of her family's death return because of him and Jose's the only one left alive present. This leads to both Henrietta and Jose dying within minutes of the resulting Freak Out, if not seconds. Dante himself is well beyond the MEH by the time he offed Enrica, her parents, and Jean's girlfriend with a single car bomb, and it's also implied due to Ski Mask Guy's presence at the Battle of Turin that Dante was also behind the murder of Henrietta's family, with everything that murder entailed. Oh, and as a final "fuck you" to the Agency? Only Rico shooting herown fratello could finally put an end to Dante once and for all.
The nameless manager of the Princess Imperial restaurant kidnaps Mitsuboshi and raped him repeatedly for a week. Her actions deeply traumatized him to the point that he lusted after Shio, believing only she could make him pure again.
Shio and Asahi's father was revealed to have crossed it earlier in his life when he raped Yuuna when she was sixteen-years-old, merely because she accidentally pushed him .
Satou's aunt crosses it in Chapter 38 when she lures Mitsuboshi into Satou's former room and attempts to force herself onto him. This is especially bad because it was Mitsuboshi's boss that caused his Start of Darkness obsession with Shio.
Inverted by Haruhi Suzumiya in the second light novel, when she and Tsuruya spike Mikuru's drink merely for the sake of realism during the shoot for her Z-grade movie, despite all the risks it could bring to Mikuru's health. When Kyon realizes Haruhi's reason for doing it, it's a Berserk Button and nearly earns her a punch in the face... which subsequently leads to her Heel Realization when she realizes that she's doing it wrong (especially in the anime, where we have her staring away from Kyon in remorse and with tears in her eyes) and then to Character Development on her part forthebetter. As for Tsuruya herself, she subverts this with a firm grasp on the Idiot Ball, as she agreed to help Haruhi put tequila in Mikuru's drink under the assumption that Haruhi wanted to improve Mikuru's acting.
Zorin Blitz crosses it when she lays siege to the Hellsing Mansion with her forces, mind rapes Seras by delving deep into Seras' memories, forcing her to relive her painful childhood, where she had to watch her parents be murdered by gangsters and her mother's corpse being raped. While Seras is trapped in the illusion, Zorin hacks off her arm, stabs her through the back, and slashes out her eyes. Bernadotte and his two remaining squad members arrive and manage to temporarily disable Zorin by shooting her multiple times and Bernadotte tries to escape with the badly wounded Seras, but Zorin kills him by stabbing him through the back with her scythe. To top it all off as Seras cradles Pip's dead body and cries for him Zorin mocks Pip calling him an "insect" and prepares to kill Seras and her fellow team members. This was enough to provoke Seras into drinking Pip's blood and becoming a full vampire before absolutely curb stomping Zorin and her forces to death and killing Zorin by cheese-grating her face against a nearby wall until it was nothing more than a red smear.
The burglars from Seras's past definitely crossed the MEH. Seras, who seems a cheerful and upbeat girl for most of the manga, has a rather dark and disturbing backstory, which seems to have happened when she was very young. It consists of her father being murdered by burglars, her mother hiding her in a cupboard to protect her, and her mother's subsequent murder by the same burglars. Seras tries to exact revenge by stabbing one of the guys in the eye with a fork. She gets shot for doing so and one of the perpetrators proceed to rape her mother's corpse, due to it being "still warm". In full view of Seras who lies on the ground bleeding profusely watching it happen and unable to do anything to stop it.
Enrico Maxwell crosses it with his orders upon arriving with his forces in London. Not content with merely fighting Millennium, Maxwell, already slipping quite badly sanity-wise, sentences everyone in London to "DEATH! DEATH! DEATH! DEATH!" and orders his men to slaughter every Protestant and other civilian in London, who are already having to deal with the ravening vampire Nazis eating them and worse. This horrific move is enough to turn his former mentor and most loyal agent, Alexander Anderson, against him, to the point that when Alucard unleashes his full power as Dracula, Anderson takes it upon himself to shatter the glass cage protecting Maxwell from Alucard's ravening familiars, leading to a well-deserved Karmic Death.
In Hi-Speed Jecy, Cross Bismarck crosses at the end of the third episode when he murders President Markham, much to the surprise of Jecy and Anita, who were trying to use the dictator as leverage against him. Jecy is quick to denounce this act of backstabbing.
Sure, that guy from the gas station did lose his mind (and explicitly admitted to being a psycho) after being forced to kill his family when they got bitten, but that doesn't excuse the fact that afterward, he tried to kill both Takashi and Rei (and rape the latter) when the two parties crossed paths. Satisfying doesn't even begin to describe how Takashi deals with the bastard.
Shido crosses it in his very first scene (if you don't count a brief non-speaking appearance in the first chapter/episode) when he kills one of his own students just before boarding the Orgybus, and he doesn't ever look back.
Shion Sonozaki torturing and murdering Satoko in the Meakashi-hen arc of Higurashi: When They Cry and forcing her sister Mion to watch. Even she admits that she's irredeemable at that point. Which is, in an odd way, why she decides to add two more corpses to the pile.
Yagi, a medium-level henchman of the final Big Bad in Holyland, crosses this by kidnapping Yuu's girlfriend Mai, drugging her, and leaving her with three of his henchmen in a situation where she could get raped easily (said drug also being an aphrodisiac) and broadcasting the whole thing live via his cellular phone to coerce Yuu into not fighting back while Yagi's thugs beat him to a pulp. Fortunately, poor Mai is rescued before anything serious can happen to her, and Yagi gets his due punishment from Yuu later.
His very first act was to use his shape shifting abilities to attack and nearly kill Kikyo while posing as Inuyasha, then pose as Kikyo and make Inuyasha think Kikyo was trying to kill him, all leading to Inuyasha getting pinned to a tree and Kikyo dying hating Inuyasha, which would bring massive trouble when she was revived.
When he finally steps out of his figurative and literal mask, when he reveals he revived the Demon Slayer Sango's brother, Kohaku to be his puppet and later revealed he's essentially blackmailing him into service in order to not Go Mad from the Revelation of being forced to kill his own clan and be Driven to Suicide.
Mortally wounding the revived priestess Kikyo, after becoming stronger and discarding his heart. This is the first time that he actually got his hands dirty and proving he's utterly abandoned his humanity.
Killing Kagura and forcing Kanna to commit suicide, his followers from the beginning merely out of sadism and to dispose of the heroes. Proving that not even his own followers are immune to his dog kicking.
The anime has one notable incident 15 years prior the plot, when he tries to murder a potentially powerful priestess as a child, on the small possibility she'd be a threat. This is extremely heinous even by his standards as listed above.
He ain't the only villain to have crossed it either, either. Shiori's grandfather crosses it to a horrifying degree when he killed his own son aka Shiori's dad for daring to bear a Half-Human Hybrid child and try defending humans.
Dario Brando crossed the line before the series even began, with the reveal that he had worked his wife to death just to have enough money to buy booze. There's a reason Dio's murder of him is considered his one justifiable action.
While Dio Brando makes it clear from his introduction that he is a horrible, horrible person, he crosses the line when he burns Jonathan's dog Danny to death out of spite after Jonathan beat him in a fight.
Tarkus crosses the line when he crushes Bruford's remains while mocking him for his weakness. Though in Jonathan's eyes, him killing Zeppeli is this, as it's the exact moment Jonathan declares that all bets are off.
Straizo crosses the line by betraying Speedwagon and leaving him to die in order to turn himself into a vampire.
In Joseph's eyes, Kars crosses the line when he uses a body double during his fight against Lisa Lisa after having previously agreed to a fair fight, as it goes against the wishes of Kars' deceased friends, Esidisi and Wamuu.
While animals usually have the excuse of not having a sense of morality, animals with Stands are granted enough intelligence to have one, so it's safe to say that Forever crosses the line when he spies on and tries to sexually assault Anne, an underage girl, while she's in the shower.
J. Geil crossed the line before the Part even began by raping and murdering Polnareff's sister, Cherie.
Similar to Forever, Pet Shop is granted enough intelligence by his Stand to have a sense of morality, so he quite clearly crosses the line by murdering two innocent dogs and then attempting to murder their owner, a child, as well.
Terence T. D'Arby is another one who crosses it before the events of the Part, when he imprisons the souls of countless victims inside dolls that he keeps as still-living trophies. Making it even worse is how he not only plays dress-up with them (including the female dolls) and is shown suggestively fondling Kakyoin's doll, but also in how he enjoys seeing their minds break over time.
If you for some reason didn't feel DIO crossed the line back in Phantom Blood, you probably feel he did when he forces Senator Phillips to drive over a sidewalk full of people. And if you somehow don't feel he's crossed the line yet, him killing Kakyoin was probably the last straw.
While Angelo definitely crossed the line before the Part even began by raping two boys and murdering another, him killing Ryohei and attempting to kill Tomoko is seen as the moment where he proves himself completely irredeemable. Notably, he's one of the few enemies Josuke doesn't befriend after defeating, and after what he's done, Josuke giving him a Fate Worse than Death is agreed to be well deserved.
In Okuyasu's eyes, Akira Otoishi crosses the line when he murders Keicho and steals the Stand Arrow, just as Okuyasu and Keicho were about to patch things up.
Diavolo seemingly crosses the line when he attempts to kill Trish, his own daughter. However, he actually crossed the line before the Part even began by burying his mother alive under his house and then burning down his home village when someone finds her.
Wu Tomoki crosses the line when he has Mitsuba unknowingly use her unborn child in an Equivalent Exchange experiment. This ends up somewhat subverted, however, when he reveals that he has no control over the results of the exchange, and that the possible death of Mitsuba's child was entirely out of his control.
Jobin Higashikatadoesn't cross the line when he kills Ojiro. After all, Ojiro came after him and his son, he was entirely in the right to take him out. However, he does cross the line when he murders Ojiro's girlfriend, Makorin, out of suspicion that she may be a threat to him (she wasn't). He also states that he would have murdered Makorin's daughter had she been a Stand User. If you don't feel he's crossed the line yet, you probably feel he did when he attempts to murder Yasuho, even after Mitsuba tells him that Yasuho helped save her life.
Kaede Sakura in Kämpfer is implied in episodes 10 and 11 to have a Split Personality. Her Superpowered Evil Side had already made herself known as callous by siding with the Moderators, but when she brainwashes Mikoto and pits her against her own friends, the Purple Betrayers, in episode 13 (episode 1 of the OVA), you realize Kaede ain't coming back from the MEH.
Kenichi: The Mightiest Disciple: While none of the YAMI masters are good guys to begin with (Affably Evil, at best), resident Pencak Silat master Silcardo Jenazad is a very special case. In order to get a replacement for his slain disciple (who he'd killed himself via avalanche several arcs earlier for disrespecting their martial art), he tricks Akira Hongo, YAMI's "God Fist," into almost killing Kenichi while the other man is locked in a duel with Sakaki AND while both men are fighting even while unconscious. He pulls this off by radiating enough killing intent from behind Hongo so that the latter will instinctively lash out in self-defense and inadvertently murder Kenichi, who's right behind him at that point, in the process. And then after that happens he takes advantage of Miu's chaotic state of mind, caused by her thinking Kenichi's dead (when in fact he's survived, but just barely), kidnaps her and systematically brainwashes her into becoming a killing machine with no memories or emotion.
And just in case you don't think the above moment is despicable enough for him to have crossed the horizon, what he does in subsequent chapters should be concrete enough evidence that he's beyond any chance of forgiveness: he aggressively pits the Brainwashed and Crazy Miu against Kenichi in a fight to the death, with the expectation that Jenazad's brainwashing of Miu will be fully and finally completed when Miu kills Kenichi, or as he terms it "destroying the last piece of her heart" so that his control over her will be absolute. And for every attempt Kenichi makes to snap Miu out of the brainwashing (and any moment Miu appears to remember who Kenichi is), Jenazad urges her more and more to press on and kill the boy. It takes Kenichi taking a third option via smashing the helmet that Miu is wearing to have Jenazad's mind control of her snap..
It's hard to say when Ragyo Kiryuin crosses this - there's her molestation of her own daughter Satsuki, the brutal beatdown she gives her in Episode 18, trying to bring about the end of the world with Life Fibers, or trying to infuse her second child with Life Fibers in-utero, and then throwing said daughter out like garbage when the experiment seemingly failed and the baby died (or so she thought). As Satsuki herself notes, she didn't even bother giving her second child a name! This was bad enough that it made both her husband and her oldest daughter turn on her (independently of each other) and secretly plot revenge.
Deconstructed in Is This a Zombie? by Yoruno, who makes it his goal to cross the MEH enough to provoke Eu into killing him. He succeeds at the end of episode 11; before Eu subsequently kills him, he reveals that his last wish is to be reincarnated as a penguin, because he likes penguins. He himself considers the death of another of Eu's paladins at his hands to be his own personal MEH.
In the Liar Game, manga, Yokoya kills his two pet mice. Until then he could have just been someone with a traumatic childhood or someone really evil, but then he just becomes a monster.
Nanoha Takamachi always does her best to understand and help her enemies, and after StrikerS, the cast is comprised almost entirely of ex-foes. That being said, when there's a character that can't be befriended, they really can't be befriended. Precia Testarossa from Magical Girl Lyrical Nanoha crosses the line by mercilessly whipping her 9-year-old daughter Fate into a state of near-unconsciousness for not bringing her enough Jewel Seeds, and then later crushes her only reason for living.
In StrikerS, Jail Scaglietti was completely fine with anything, so long as it justified his research into cyborg bioweapons. Although he never explicitly crossed the line, his tendency to laugh maniacally while watching people suffer put him past redemption, even by Nanoha standards. His Dragon Quattro, however, did cross the line when she strapped the innocent Vivio to the throne powering the Big Bad's Cool Starship and tortured her into almost insanity to power it, and then forced her to try and kill her adoptive mother with her bare hands, while taunting them both. Quattro was punishedaccordingly.
In Force, Cypha crosses the Moral Event Horizon by admitting to killing dozens of civilians without any hint of remorse — just before almost killing fan-favorite Signum.
Grace O'Connor in Macross Frontier has a number of candidates, with conducting painful, potentially instantly fatal, and certainly eventually fatal experiments on a seven year old girl probably close to the top of the list. Made worse when they call the little girl Subject Fairy-Nine and Fridge Logic sets in with "Wait, what happened to Fairies One through Eight?"Even then one of the drama CDs suggests an opening for redemption with Grace when she realizes that in the ten years she spent practically raising that girl (whose name is Sheryl Nome) she's developed strong feelings for her, no longer just "Fairy-Nine" but "her little fairy." She decides that the feelings will get in the way of their plan, so she deletes them with cybernetics in one of the most subtle crossings of the Moral Event Horizon ever.
Many horrible things happen throughout the show but Bondrewd Lord of Dawn and his horrible experiments are the worst. His first action is the Elevator scene which is where Bondrewd is forcing Mitty to take the 6th level curse (Which is Body Horror incarnate) and make her suffer A Fate Worse Than Death while having Nanachi being Forced to Watch, Bondrewd later decides to torture Mitty later on. Nanachi is later forced to make Reg kill Mitty with the Incinerator so Mitty can't suffer anymore.
In Muhyo and Roji, the final revelation that puts Teeki over the Moral Event Horizon is the revelation that he was responsible for Enchu's mother's death, causing his Start of Darkness and thus most of the conflict in the story. To a lesser extent, his responsibility for Rio's mother dying also applies.
The Fourth Kazekage crosses the MEH with his treatment of his son, Gaara. He has a demon sealed into the boy at birth, completely isolates him from his family save for his uncle Yashamaru, who he then orders to attempt to kill Gaara and tell him that both his mother and he, Yashamaru, the only person to ever love Gaara or show him kindness, hated him to the death. Just to see what happens. Yashamaru did so against his will, and promptly killed himself to clinch it. And when the emotionally fragile, socially isolated child reacts badly to the fact that no one's ever loved him, he decides to have the kid murdered. No wonder Gaara turned out like he did, at least until Naruto intervened in his life. It's so bad that the Kazekage actually comes to admit that he was a total bastard after he's revived via Edo Tensei and Gaara dealt him a massive and magnificent call-out.
Danzo did this in the backstory, when he set up Kabuto and his mother to kill each other. Good intentions or not, that is horrifically cruel.
Though he was outclassed by Orochimaru in the following arc, Gato crosses the line when he brutally murdered Kaiza in front of the Land Of Waves. He also is responsible for driving said land into poverty.
Nearly everything that Orochimaru does, but the kidnapping and experimenting on multiple people, callously discarding them when they became unnessary and taking over their bodies, takes the cake.
Hidan crosses the line when he kills Asuma Sarutobi, and later mocking his student Shikamaru over the act.
Black Zetsu with his manipulating Indra and other Uchihas, being at least partially responsible for their Curse of Hatred, instigating wars and conflicts all to free Kaguya Otsutsuki, also deserves mention.
Obito Uchiha crossed this line when he released the Nine Tailed Fox onto the Hidden Leaf Village. Watching with sick amusement behind his mask while Ninja and innocent civilians alike were being slaughtered by the dozens. Somehow outdoing his earlier crossing of threatening a newborn Naruto's life just to separate both of his parents.
Gendo Ikari, leader of NERV and Shinji's Jerkass father. Many of the things he's done through the series were questionable, but he would cross the line when, following Shinji's refusal to destroy an Angel-possessed Evangelion Unit-03, he activates the dummy-plug system to carry out its destruction, nearly killing its pilot Toji Suzuhara, Shinji's classmate and friend in the process. This is taken Up to Eleven in the manga where the pilot actually dies, and becomes all the worse still in Evangelion 2.0, where Shinji's hands are practically bolted to the controls while the dummy-plug destroys Unit-03 and almost kills its new pilot, Asuka.
To some, Ritsuko Akagi crosses it when she destroys the clones of Rei simply out of insanity and jealousy. She's deeply aware of how low she's fallen and begs Misato to kill her when she's done.
Him and SEELE had pretty much already crossed it years ago, when they through their machinations deliberately caused Second Impact, which resulted in a death-toll in the ballpack of 3 billion people.
During his review of End of Evangelion, Bennett the Sage discusses this trope, positing that Shinji crosses it during the infamoushospital scene, which he finds repulsive and believes pushes Shinji out of "unlikely hero" territory and into "complete douchebag"—something Shinji even admits In-Universe.
Shinji: I'm the lowest...
Peach Girl: Kairi has a trio of obsessive clingy jealous girls who once attacked Momo and threatened to set her on fire if she continued taking up Kairi's attention.
A demon lord and her minions attack a village in Problem Children Are Coming from Another World, Aren't They?: destroying things, trying to kill people, using mass hypnosis, the usual. Then Kurousagi stops the battle for supposed misconduct... which turns out to play into their Batman Gambit. The demon lord is apparently Pestilence, and she has infected most of the village with the plague, intending to delay the match for an entire month so that most of her opponents will die slowly and painfully before the battle technically begins. Just in case you were underwhelmed by the actions of the bad guys so far...
In Penguindrum, Sanetoshi had done plenty of shit, but he seriously crossed the MEH in episode 23. He didn't just do it by revealing that he was the one who "killed" Momoka via transforming her in the two Penguin Hats when she tried to stop him from destroying the world (thus causing a good part of the events of the series to take place), but by first strengthening Kanba's FaceHeel Turn via forcing him to see Masako die and then reviving her while promising to do the same to Himari if he destroys the world for him and then by setting up Ringo to be seriously injured and mocking her as she was burning to almost death, in his quest to destroy the Destiny Diary.
Kyubey, the Weasel Mascot from Puella Magi Madoka Magica comes close a couple of times in his Kick the Dog moments, like during the penultimate timeline in episode 7 when he manipulates Sayaka's soul gem so that she feels excruciating physical pain, just to drive home the truth about how becoming a magical girl turns you into (as Kyoko pointed out) a walking corpse by default. But he plows over the Moral Event Horizon in Rebellion; unlike in the series, in which the only way to get that vital energy was to meticulously break these girls, Kyubey had a way to fulfill his mission with the Law of Cycles. Unfortunately, the little bastard got greedy, so he decides to bring back the witch system and all the misery that comes with it, fucking over everything that Madoka did, simply because it's a bit more productive for him.
In Puella Magi Oriko MagicaKirika Kure may have crossed it when she released a Charlotte-like witch in the cast's school, which proceeded to eat Kazuko-sensei alive and slaughter many other innocent students. Oriko, a well-meaning magical girl who is herself no saint, is more of a subversion, since she uses dirty tactics only because she believes such tactics are the only way to save the world (and she truly believes that Madoka becoming a magical girl means game over for everybody). Alas, that was her own pride talking to her and blinding her to the truth—Madoka's ultimate role was not to destroy the world, but to save it. It's absolutely no wonder that in the afterlife, Oriko looks very depressed and remorseful - she likely realized how badly she fucked updue to her own pride.
Psycho-Pass has latent criminals crossing the line which makes them easy targets for lethal elimination by the bureau. But there are those who stand out:
Shogo Makishima, the Big Bad of Season 1, is known to be The Corrupter, The Sociopath and one of those responsible for Mitsuru Sasayama's death which resulted to Kougami's demotion to Enforcer. But his first onscreen MEH is killing Akane's friend in front of her after she failed to shoot him. Though that earned him some leather pants and many believed that his MEH is planning to sabotage the food supply and killing Masaoka.
Kirito Kamui, the Big Bad of Season 2, made this his Establishing Character Moment by kidnapping an Inspector and forcing her to kill her Enforcer. If that's not his MEH, then taking one of her eyes out and manipulating her to call her partner which got several hostages including the partner brutally killed just to get the Dominator is this.
Sakuya Togane already crossed the line in the past where, as a child, he killed a puppy for his mother's experiment. Then, he kills Akane's grandma with the Dominator just to darker her hue.
Kobuo Oguro may elicit some sympathy at first, as a Salaryman who gets treated like a criminal from one bad Psycho-Pass, but he loses it when he rapes his hostage.
Allegedly crossed by the high school basketball team captain by propositioning a minor, which sets the plot of Ro-Kyu-Bu! in motion as the entire team gets punished for his alleged crime (which hasn't been proven as of the current episode), forcing the main character to coach a girls' basketball team consisting of grade-schoolers in an example of misplacedLaser-Guided Karma at work.
Hitomi Ishigami virtually blowing up the whole school with a magic mirror toward the end of the first serialization. She gets her comeuppance yet again when she's arrested for the crime. Her motive for doing this was a revenge scheme against the Newspaper Club for exposing her plot to turn the most beautiful female students into stone and use of modeling sessions as a pretense and getting her fired for it. So in other words, she wrecked Yokai Academy out of spite toward just a few of the students. It's also arguable that she may have crossed it earlier when she schemed with the Security Committee and Kuyou to murder Tsukune for the same reason.
Kuyou himself crosses it with his interpretation of the school rule "No humans allowed" as "Death to all filthy human spies!". Not only is he willing to commit murder based on his own twisted interpretation of a school rule, he's also completely willing to risk the lives of the existing members of the Security Committee by having Tsukune murdered. To make his mindset much worse, if Tsukune died and the Security Committee was eventually caught, Fairy Tail would've won.
Kanade Kamiya has a lot of potential crossing points, but it's most likely that he crossed it by killing Marin Kawamoto's husband in front of her. To make masters worse, he had no reason to kill said husband or any other humans he did at the time; he went on a mass-murdering rampage, in his own words, simply to pass the time and clear his head.
Gyokuro Shuzen is a nasty one, and her sadistic treatment of Moka just a chapter before was bad, but when she, without a single ounce of hesitation or regret, orders Kahlua to kill her own beloved little sister Kokoa? And remember that Gyokuro is Kokoa's birth mother as well, and Kahlua was so horrified by the order that she literally begged Gyokuro to change her mind.
It's possible that Hokuto and Kiria may have crossed it during the festival arc. Hokuto chains up all of the harem (with the exception of Moka who had been kidnapped) inside a barrier created by Mikogami's rosary so that they don't stop him. Tsukune tries to fight him but he keeps getting knocked down and beaten to a bloody pulp right in front of his friends. Kiria's was when he had Moka. He told her that he would let her go free if she removed her rosary by herself (back then only Tsukune could do that). To motivate her, he gave her a live camera feed on Hokuto beating up on Tsukune. Basically it boils down to, "Do the impossible bitch, or your boyfriend is gonna be paste."
Ultimately subverted with Lady Oyakata; she seems to have already crossed it by her own admission, but Ruby, her former disciple, refuses to believe it even after Oyakata critically wounds her during the boss fight and even saves Oyakata from certain death when her binding spell backfires on her. Oyakata repays the favor by using the last of her life force to sufficiently heal Ruby.
If, after all he had done and what was revealed about him, you still had a small shred of hope for Miyabi Fujisaki, that went out the window the moment he murdered Outer Moka in cold blood by destroying Moka's rosary.
Nagare Kano is already well past the MEH by the time he appears, but blackmailing a girl into bailing on the Newspaper Club for him when they're in a deadline? Putting the Newspaper Club's hard work at risk over your lust!? Calling this Kodak fiend a pervert at this point would be an insult to perverts everywhere.
Alberich from the Asgard arc of Saint Seiya. While all the other God Warriors were following Hilda out of loyalty and love for their country, Alberich is happy to reveal he knew all along that Hilda was being controlled by Poseidon, and that he let the war go along so he'd claim all his colleagues' Saphires of Odin after they were killed, and then get Balmung's Sword and take over the world.
Dr. Katsuragi of Sakura Gari is pretty fond of doing horrible things. In the backstory he persuaded Souma (who was angry with his abusive stepmother, Sakurako) into wanting to kill her: he drugged Sakurako when she was taking a bath, took Souma there and told him to kill her as revenge for his abuse, and when Souma couldn't go through with it he grabbed Souma's hand, put the knife forcefully in it and forcibly made him cut Sakurako's wrists, effectively killing her. Then, he rapes Souma almost in the spot. When Souma confronts Katsuragi on his rape and torture of Masataka, Katsuragi denies the accusation and tries to seduce Souma. He acts uninterested and mentions Masataka's name, so Katsuragi actually grabs Souma by the throat and tries to strangle him. And then karma meets up with himSpectacularly.
To a lot of people, Hatori from Sekai Ichi Hatsukoi crosses the line when he brutally raped Chiaki in the novel. The anime was nice enough to tone it down but said fans aren't going to let what happened in the novel slide and it implies it in the anime as well. Being a Karma Houdini and beating up on Yanase when the guy broke down crying after Chiaki rejected him a third time and refusing to believe that his friend has feelings for him does not help his case in trying to redeem himself.
Soul Eater: While she had committed some other terrible acts before this point, Medusa's Moral Event Horizon is generally cited as when she claimed that Crona, who she had been abusing and experimenting on for her plan to resurrect an Eldritch Abomination, is really her child; she doesn't get any better from there. Also, Giriko jumped over the line when he tried to rape Maka in the book of Eibon, when she's at her lowest point; previously, he was just another of the ineffectual minor villains.
Despite his pre-Face-Heel-Turn-reveal murder of BJ and moment of sadistic enjoyment at Kid's pain, Justin could have been seen as redeemable, especially since it was strongly hinted that Clown had something to do with his betrayal. However after he killed Tezca who deceived DWMA and put his life on line to offer a chance to return on top of friendship, it was pretty clear that Justin was not coming back to the good side. He even got a permanently burning flame on his face from the fight, in a chapter named Hellfire.
Strider: Matic never hid the fact he was not nice, while secretly in line with the Enterprise and their Mind Control weapon. Then, he reveals to Hiryu that he set him up to kill all the figureheads of Enterprise so he'd have free way to claim their weapon, AND that he'd have the Striders' senile director killed and Hiryu and his friend Kain framed and executed for it. And even then, there's is the fact that he has known of the Zain Project for 3 years, implying that he staged the brainwashing of Hiryu's sister by Enterprise 2 years ago, which lead to her murdering 10 Strider trainees and Hiryu being forced to kill her, prompting his retirement.
Yuka is revealed to have crossed the line long ago: she was never in a relationship with Shinji and was the one who started the fire at the movie theater believing that she could have Shinji even if he was dead.
Tsuruoka has different candidates for this: he was the one who arranged for the death of Nana's parents and created the child soldier program making him directly responsible for Nana's actions on the island; he held Moe's grandmother hostage to keep Moe under line; he shot Michiru twice in the head to prevent her from healing herself all to ensure that Nana continued to kill for him; and he brainwashed a vengeful Nanao into becoming a pawn.
Tokyo Babylon reveals that Seishirou is the Sakurazukamori assassin who had no qualms of killing people and is the one who put the pentacle marks on Subaru's hands in the first place. But killing Hokuto proved that he's no longer the Nice Guy that Subaru loved anymore which is so tragic.
Tokyo Ghoul gives us the following vile moments that crossed the line:
Yamori was pretty much tiptoeing the line to begin with, being a Torture Technician that straps Kaneki to a chair and begins torturing him for several days. But when he realizes that physical torture isn't breaking his latest toy fast enough, Yamori brings out his trump card. He'd captured Kaneki by promising to let his friends go, but kept the other imprisoned elsewhere. He brings up two of the prisoners, a mother and her young son, and orders Kaneki to decide which of them will die. Even Yamori's Living Emotional Crutch, Nico, protests that this is taking things too far and attempts to talk him down. This, combined with Kaneki refusing to "play along", causes Yamori to throw a temper tantrum and strangle the child to death before killing the mother.
Kureo Mado is established as a sadistic Investigator that takes pleasure in tormenting Ghouls, expressing disgust when they "imitate humans" through selfless actions or compassion. He starts things off by killing a gentle Ghoul, Ryouko Fueguchi, having made certain she realizes the weapon he's using was made from her late husband's corpse. But he really crosses the line when he lures her 14-year old daughter Hinami into a trap by taking advantage of her superior sense of smell — he leaves a bag for her, which contains Ryouko's forearm. Once he's trapped her and her violently protective Cool Big Sis Touka, he taunts her further by showing off his new matching set of weapons, made from the bodies of her parents. Even after all the vile things he does, Hinami still refuses to take revenge and is prepared to spare him — he takes the chance to attempt to kill her, and dies for his effort.
The Twelve Kingdoms has more than one person, specially the sen-nin or immortals, cross a few of these:
King Chuutatsu: Being cynical and upholding the rules didn't make him evil. There WAS lots of corruption in Hou, after all, and as a former government officer he knew that well. Slaughtering around 10% of the population over minor offenses, and then more after his kirin fell sick in an attempt to make things even? THAT is what made him an asshole.
Queen Kekai: Her and Chuutatsu's daughter had a nice little friend, so sweet and elegant! And wait, was she better at everything than the Princess? How dared she! So Kekai got her out of the way.... by falsely accusing her mother of accepting bribes, thus tricking her husband the King into having both mother and daughter executed. THAT would teach them!
Governor Atsuyu: He had a subordinate named Kouya, who also was the master of a certain demon. But when said kid had some people killed and eaten and was then horrified at what he had done... what did Atsuyu do? He told Kouya it's okay and had him "groomed" into a bastard who'd kill his enemies for him while he made himself look all saintly! Eeeeh...
Riyo: At some point, she took a girl from Hourai who couldn't speak the language and was completely lost... Why, Riyo immediately started humiliating Suzu by re-naming her "Mokurin" ("Fool" in the local language) and abused her psychologically and physically for 100 years straight! "Punishing her for her sins", indeed.
Shokou: He admitted he was in For the Evulz, and as such he oppressed the place he was in charge of as Governor. And not only he manipulated a kid from Hourai (who happened to be both a friend of Youko and Yuka's boyfriend) and kidnapped Old Retainer Enho (with his guards murdering his maid Rangyaku too, and the maddened Hourai kid shooting her brother Keikei almost to death), but he also intentionally ran a blinded kid named Seishuu over with his carriage, killing him, and laughed about it. What the....
The King of Kou: Okay, this one was insecure about the taika-led kingdoms like En, and then two taika girls with potential to become the Queen of Kei arrived. What did he do? He manipulated Yuka to pit her against Youko, playing on her feelings of insecurity for his benefit. And once Yuka lost against Youko, he immediately tried to kill Youko himself. No, just no.
In Umineko: When They CryRosa Ushiromiya either seriously kicks the puppy or downright crosses this when she rips Sakutaro in half. Though it seemed minor at first, you would recall that she gave Maria the stuffed lion in the first place, and that Maria considered (or made) him real, and that he was probably her only friend. She also "kills" one of the Siesta sisters, though inadvertently when she threw her on the ground. And often at times where she slaps Maria. Yes, you should show your child discipline, but when you take it too far, it is just abuse. And she often claims to have to go to work, but in reality, she goes to spend the night with one of her boyfriends — meaning she would often leave Maria home alone, often to the point where she would have to go out and get her own food. She even left one boyfriend when he told her to spend her time with her daughter. But what ultimately made her cross the horizon would have to be when she told Maria that she never loved her and wished for her to have died, so that she would have a happy life. She even tells her to go to Hell. Though, given her status as a Tragic Villain, a victim of abuse and bullying from her own siblings and her father (which Rudolf actually aknowledges), the local Chew Toy, or most likely just stressed at work, she might subvert this trope. Though, Beatrice was disgusted by her behavior.
She actually does, because Rosa is the very strange case of an abusive mother doubling as Mama Bear. In EP-2, she faces the goat servants on her own to protect herself and Maria, taking them with pens to the eyes and shotguns; in Episode 8 of the game, she shoves a rifle down Erika's throat when she mocks Maria and tells her that her mom will abandon her. Several of the episodes described here happen in different timelines (and the one described at the end happens only in EP-4), thus how abusiveor nurturing she is can seriously vary depending on which EP we're talking of.
Eva-Beatrice crosses this when she repeatedly murders both Rosa and Maria, purely for her own amusement, and in very creatively cruel ways. She really crossed it when she was supposed to murder a person once in the Twilight. She actually gets so bad that, again, Beatrice is squicked out and disagrees with her.
Bernkastel does truly horrible things, but in EP7, she shows Lion Ushiromiya the miracle of his/her existence, and then proceeds to force Lion and Ange to watch a horrible scenario in which Ange's parents are the murderers. Ange is unable to handle this, and as such she is once again torn to pieces. When Lion tries to give Bernkastel a What the Hell, Hero? speech, Bernkastel shows Lion his/her eventual fate- being massacred along with the rest of the family on October 4th and 5th, just like in all the other universes. Bernkastel laughs at Lion's fate, and she is unwilling to let Lion escape.
Kinzo also crossed it when it was revealed that Yasu, aka the real persona of Beatrice, Shannon and Kanon is actually his child fathered on his own daughter Beatrice, who he kept isolated and eventually raped because she resembled her mother, Kinzo's deceased mistress. Can you say "Just like Noah Cross"? Good.
Swordfish does this a few times in Under Grand Hotel especially him raping his lover Sen to almost death when Sen said something that annoyed him.
In Wolf Guy - Wolfen Crest Haguro Dou manipulates the younger Kuroda into going Columbine on half the student body out of vengeance against Inugami for his brother's death. Using weapons from his family gun cellar. The kicker? His brother died because HAGURO pulled his life-support.
Also, Haguro beat his subordinate Chiba within an inch of his life, biting off his tongue, and then raping him for good measure to the point that Chiba ends up dying from a combination of ruptured organs, blood loss, and broken ribs. Thankfully, Inugami gave Chiba some of his blood which ended up bringing Chiba back to life. Why did Haguro do such a thing? Because Chiba ended up encountering Inugami out on the streets and talked to him for maybe 15 minutes when Haguro wasn't around. Haguro is Yandere for Inugami's werewolf form, you see.
Wolf's Rain: Darcia crosses it when he kills Toboe. Said character is the most innocent in the story, and is still just a child at the time.
X1999. By the time Kamui decided to join the Dragons of Heaven, Fuuma joins the other side and kills his own sister, Kotori, while Kamui is Forced to Watch. The manga is more brutal that he beheads her!
Satsuki crossed it by killing Yuzuriha's dog spirit, Inuki, after the girl failed to answer one simple question.
In the movie, several Dragons of Earth crossed more lines here where Yuto and Kusanagi killing Yuzuriha and Fuuma killing his own members (including Kanoe), fatally stabbing Arashi as she watched Sorata die and pulling out the Shinken from Kotori which resulted to her death.