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.
- Photo: Toei Animation
As A Villain: Yamcha was once a desert bandit who was actually a credible threat to Goku. He even managed to defeat Goku in his Great Ape form! He wasn't exactly a villain anymore when he did this, but he hadn't yet undergone the embarrassing transformation he would once he joined the good guys on a more permanent basis.
As A Good Guy: You've all seen the memes - Yamcha has a reputation as not just one of the weakest characters in Dragon Ball, but one of the weakest characters in anime, period. While this is definitely an exaggeration, he pretty much never gets the chance to do anything cool, is usually the butt of jokes, and doesn't hold a candle to most of the other fighters. It's hard to feel too sorry for him considering his nasty attitude towards women, but it's still a little sad.21727Big power demotion?
- Photo: Studio Pierrot
As A Villain: Orochimaru used to be one of the most terrifying villains in Naruto. He not only performs horrific, life-ending experiments on children, he also uses creepy snake-based jutsu, body hops from one host to the next, and is so strong he resists having his soul removed by the King of the Underworld.
As A Good Guy: In the Boruto timeline, he's content to hang out in his lab making artificial humans for an unspecified purpose. While he likely still has access to the Jutsu he used to use, he's rarely seen actually fighting. What's more, his experimental capacity is limited by the fact that he's being monitored by Konoha ninja. This happens because, while he's largely committed to getting along with the heroes, few people trust him to have truly given up his former villainy.16754Big power demotion?
Itona Horibe - Assassination ClassroomPhoto: Lerche
As A Villain: After Itona was abandoned by his father, Shiro found him and implanted tentacles into his body, giving him speed, strength, and resiliency that was almost on par with Koro-sensei. Shiro uses him to lure out Koro-sensei.
As A Good Guy: Once Itona is defeated, his tentacles are removed and he becomes a permanent member of class 5-E. All of his powers are gone. While he does participate in a few future battles, he takes a backseat role to characters like Karma and Nagisa. The tentacles were dangerous, so the power boost they provided wasn't worth it, but it's still very much gone.8421Big power demotion?
- Photo: Toei Animation
As A Villain: When Ken Ichijouji is trying to take over the Digital World as the Digimon Emperor, he's easily able to mind control most Digimon with his Dark Rings. He's one of the most dangerous foes the Digi-Destined have ever faced.
As A Good Guy: Once Ken realizes that he's actually hurting sentient beings instead of playing a game and gets a handle on the Dark Spore infection that was impacting his behavior, he has a breakdown and becomes one of the good guys. When this happens, his skills in just about everything, from doing schoolwork and playing soccer to fighting villainous Digimon, plummet.
This may be because of the absence of the Dark Spore, which is said to have given him his genius abilities to begin with. It might also be because his improved emotional state means he's not feeling as much pressure to be perfect, or because he just isn't using the powerful Dark Rings anymore.6422Big power demotion?