History MotiveDecay / AnimeAndManga

** After the aforementioned event in addition to [[spoiler:Nunnally's apparent demise]], Lelouch, who prior to the betrayal had actually assembled a legitimate front in the UFN to battle Britannia, now decides to go it alone, [[TheUnfettered abandoning all personal inhibitions]] and willing to use his geass on anyone and go to even more drastic extremes, including making {{Faceless|Goons}} SlaveMooks out of his new army, detonating the world's biggest energy reserve [[InferredHolocaust and apparently causing more death and destruction than he did during his rebellion pre-betrayal]]. The latter (or former technically) was at least somewhat justified because of [[BlackAndGreyMorality the opposition he faced off against]]. It's not that he became evil per se; the plot justifies it as [[spoiler:him centering the world's hate around him for world peace]]. However, given the leading circumstances and the plausibility of such a plan (and Lelouch's own admission that it was a gamble), it all seemed like a convenient [[DeathSeeker death wish]] for him. The aforementioned fact that causing worse, unnecessary destruction was a path to atonement, even as a mask, when it is even noted in side materials by Lelouch that there are other methods, makes it seem more a case of {{Designated|Evil}} than NecessarilyEvil.

* Suzaku Kururugi in ''Anime/CodeGeass'' starts off as a heroic upstanding fellow, who wants to change the [[TheEmpire system]] from the inside. After the [[spoiler:death of Euphemia at the hands of Lelouch]], he more or less seems to go temporarily insane, leading to a justified battle with the MagnificentBastard Protagonist Lelouch. However, in the interim between both seasons going well into R2, not only has he become a {{Jerkass}} of ridiculous proportions, he has sold out his old best friend for a step up the power ladder, and his goal of changing the system from within has degraded to making his own homeland a better place (effectively giving the rest of the enslaved Areas of Britannia the middle finger). [[spoiler:He does eventually realize that prioritizing means over ends ''really'' doesn't pay off after a couple of MyGodWhatHaveIDone moments and proceeds to team up with Lelouch to save the world and [[TheAtoner atone for his sins]].]]
** The Black Knights undergo a similar one in R2 19 when they [[spoiler:intend to sell out Lelouch to Schneizel]] in exchange for Japan, at the expense the rest of the world represented by UFN, for which the [=BKs=] made up the primary military force, and their fight against Britannia's dominion of the world, and there was no actual guarantee that Britannia would keep their hands off of Japan once and for all. (And their own ally Kallen was nearly caught in the crossfire.) None of this went very far at all, given that Lelouch was whisked away by Rolo in a [[spoiler:HeroicSacrifice]] the moment things started to go south, and Xingke and Kaguya would soon catch Ohgi trying to cover the whole thing up.

* Invoked over the course of ''Manga/DeathNote''. [[LightIsNotGood Light Yagami's]] megalomania causes him to completely lose sight of his original goal ([[UtopiaJustifiesTheMeans to improve the world by removing its criminal element]]) and degrade into using the Death Note to [[AGodAmI become "The God of the New World" and destroy his enemies]], as well as clean up any undesirables; by the final chapters, he's starting to kill people for being ''lazy''. He also turns from a ManipulativeBastard who carefully plans everything out into a SmugSnake who is so sure of his own success that the very concept of his own failure seems to confuse him. Many a character points out that Light is little better than a serial killer by the end, but Light's so blinded by his pride that it takes [[spoiler:his impending death]] for him to catch on.