As once pointed out by Riku, once you have gone too far in evil, there's almost no coming back.
Original villains
- Ansem (actually Xehanort) definitely crossed this line in the original Kingdom Hearts when it was revealed that he experimented on living people just For Science!. And it was outright stated that the experiments caused their hearts to collapse!
- Marluxia, the one who is placed in charge of Castle Oblivion, is very manipulative to all he meets, including his fellow members stationed with him there, if forcing Vexen to fight Sora by exploiting his fear of "The Superior" is ample evidence. To make matters worse, he plotted to take control of the Organization for himself with Larxene tagging along by having Sora lose all of his memories and make him his puppet, intending to use him to defeat all of his colleagues; the fact that Sora is still a kid only causes his morality to be confirmed to be downright evil. His treatment of Naminé isn't all that better; he doesn't care about her personal space, constantly abuses her verbally and tries to use her as a Human Shield when brawling with Axel (and he does the same during his final battle with Sora in the manga adaptation).
- Ansem's former self Master Xehanort has done a lot of bad things throughout his life. For his MEH, take your pick:
- When he extracts the darkness from Ventus and creates Vanitas;
- His Obviously Evil Gaslighting of Terra;
- When he kills his own boyhood friend Eraqus;
- Finally possessing Terra’s body;
- His defeat leading to leaving Aqua in the Realm of Darkness for a decade;
- When his younger self traveled into the future and destroyed Sora's heart. Or earlier, when he almost suffocated the boy.
- When he kills Kairi in III;
- The fact that he did all of the above (and then some) with simply a gleeful attitude. You cannot help but agree with most fans that in the end, he should have gotten a harsher fate.
- Terra-Xehanort crossed this when he uses chains against Aqua and Ventus during the Second Keyblade War, and tortures them casually, making it look like the two of them had been hanged. For Ansem's Guardian, this was the last straw, and he broke free of Terranort's hold to save them, which leads to Terra retaking his body from Xehanort's possession for good.
Disney Villains
- Multiple Disney Villains have crossed the line, but the moment they crossed it is often the same as in their source films. This is not the case with Jafar, Lady Tremaine, Scar, Clu, and Maleficent; all of them have committed acts so heinous that they're viewed as managing to become even bigger monsters in this franchise than they are in their films.
- Clayton crossed this after being caught trying to shoot Terk, leading him to stake his life on gorilla genocide, attracting the Heartless. By the climax of Deep Jungle's arc, he's succumbed to darkness, and Tarzan claims "Not Clayton. *&&X% (heart). Not Clayton," signing Clayton's death warrant. Clayton's role in the game is mainly to demonstrate how easy it is to fall to darkness, and even the other villains dismiss him as a weakhearted fool motivated by greed and wrath.
- Jafar crosses this line when he orders Genie to show him the Keyhole for Agrabah. Had Sora not shown up, the end result of this would amount to genocide, as the world would've been destroyed by the Heartless, and everyone in it would have been killed, which is what Jafar wanted. He is far worse in Kingdom Hearts II, where he becomes an Omnicidal Maniac bent on destroying the entire universe.
- Pete teeters on his line when he teams up with Barbossa and exploits Will Turner's demands with a Loophole Abuse, securing a win, and leaving Sora and his allies tied up on a ship rigged with gunpowder. Barbossa also crossed the line as well from Sora's point of view, vowing to never trust pirates again. Sora and Barbossa remain enemies when they meet again in Kingdom Hearts III.
- Lady Tremaine and her two daughters cross the line together when they outright try to murder Cinderella with an Unversed which was summoned from their hatred towards her. The monster drops a bomb on them as part of their damnation, and Aqua implies they became Heartless.
- Scar might be operating on a smaller scale than Maleficent, but he still manages to be her equal in viciousness. Aside from his canon atrocities, he crosses the line when he gleefully tries to eat Sora shortly after the latter arrives in his world. What makes this particularly vile is Sora is in the form of a Lion Cub, so Scar essentially wants to cannibalize a child. It's also worth mentioning that he's the only character in the series so far other than Xehanort that's been able to keep his original form as a Heartless.
- Clu crosses the line when he forces Sora to fight Tron/Rinzler, then kills the latter after the battle.
- However, all of this amounts to nothing compared to the actions committed by Maleficent throughout the entire franchise. She's single-handedly responsible for hundreds, if not thousands of worlds being destroyed, and the deaths of billions of innocent people; a record unmatched in Disney history until the Starkiller Base and Thanos. She's kidnapped girls whose hearts are pure light and forced them into deep sleep until all seven of them are brought together for universal domination (or worse, the end of reality itself). And she's even tricked Terra into stealing Princess Aurora's heart, and is in direct league with Xehanort.
- Prince Hans keeps the same MEH as in the film, but this time, his frozen heart causes him to become a werewolf Heartless called Sköll so he could destroy Arendelle and plunge all worlds into darkness by eating light. Hans is killed by Sora as a result.
