When some anime villains get redeemed and join the good guy's team, they use the strength they once unleashed on the heroes against their now mutual foes. But as cool as that is, it's definitely not the case for every villain-turned-hero. Some of them become far weaker than they used to be. This usually occurs in order to handle power-scaling problems: if the former villain who gave the hero so much trouble stays as strong as they were, how are future villains going to seem challenging? Also, it's not implausible that a redeemed villain would be reluctant to act as violently as they did before.
Anime villains who became weak can be frustrating. It can be disappointing to see formerly powerful villains look tame by comparison. On the other hand, it can be interesting to see a new side of them. It all depends on how it's executed. Nico Robin from One Piece gets de-powered, but there's a good reason for it and she continues to be a great character. Meanwhile, it seems like Yu-Gi-Oh! 5D's just didn't know what to do with Aki Izayoi after she joined Team Yusei.
Shishiwakamaru - Yu Yu HakushoPhoto: Sunrise
As A Villain: During the Dark Tournament, Shishiwakamaru nearly destroys everybody in the audience by summoning the souls of the deceased and letting them go on a rampage.
As A Good Guy: He doesn't exactly become a good guy, but he shows a lot less interest in senseless violence, trains under Genkai to enter the Three Kings Tournament, and is generally chill with Yusuke and company. The thing is, most of the time that he's actually being sort of nice, he's also transformed into a tiny little creature. He seems a whole lot less edgy than when he was using moves like Baku Tō Doku Shoku Sō, which is translated as Vomiting Explosive Skull Ramming Burial.4020Big power demotion?
- Photo: Studio Deen
As A Villain: Sagara Sanosuke worked as a mercinary in order to vent his frustration and rage after the Sekihō Army is destroyed by the Meiji Government. Despite Kenshin's legendary abilities, he truly struggles against him.
As A Good Guy: Sanosuke repeatedly faces opponents that defeat him with barely any effort. He realizes that he has a long way to go if he wants to achieve his goals, and uses these losses as inspiration to train harder and improve his skills.6248Big power demotion?
Satsuki Kiryuin - Kill La KillPhoto: Studio Trigger
As A Villain: Satsuki has actually always been on the good guy's team, but for most of the series nobody knows it, so she's still filling the antagonist's role. And with her iron grip on Honnōji Academy's Student Council and her mastery of swordsmanship, synchronizing with her Kamui Junketsu, and more, she's one hell of an opponent.
As A Good Guy: Once she's up against the true villain of the series, her mother Ragyo, she gets her butt handed to her. That's definitely not the first time she suffers a loss, either. It's a fall from grace, one that seems calculated to keep Ryuko the star of the show.3832Big power demotion?
- Photo: Studio Gallop
As A Villain: Aki Izayoi was driven to villainy because of her dangerous ability - the power to physically manifest Duel Monsters and their effects. Everyone treated her like a freak who could destroy them at any second, which made her vulnerable to manipulation by Divine. But despite being vulnerable, she was strong as hell, and nearly impossible for even the best duelist to deal with.
As A Good Guy: Eventually, Yusei and friends manage to persuade her to join the good guys. She's certainly a lot happier working with them, and she does start learning to control her abilities more effectively. But once she's a part of the team, the spotlight rarely hits her. Instead, she takes a backseat to characters like Yusei, Jack, and Crow. Female characters in older shonen series often meet this fate, but that doesn't make it any less frustrating.4138Big power demotion?