Shonen anime generally fall into the same trap. How do our heroes going to defeat the all-powerful villain? The trope general requires a hero of modest beginnings and his friends to travel the world trying to either stop a villain from gaining more power or getting released. In order to keep the series interesting, the villain is giving some kind of handicap to give the opposition a chance. This also happens to heroes sometimes, otherwise, the series would be boring if the hero won with one punch (LOL).
In Soul Eater everyone has a handicap
All the characters in Soul Eater have some handicap that prevents them from being as strong as they possibly can. Black Star has a tendency to show off, preventing him from being an effective assassin. Death the Kid has a weird symmetry fetish, Stein goes insane, and Shinigami cannot move from the spot he’s standing on.
Sesshomaru’s One Hit Kill
In Inuyasha, Sesshoumaru acquires a sword that can kill almost anything with one hit. This proves to be a problem for Naraku forcing him to kidnap Rin to prevent his destruction. The show ends if Sesshomaru gets his way right. Besides, Inuyasha is the star of the show and must defeat Naraku.
Orihime’s personality
In Bleach, Orihime possesses the power to “reject physical events in a manner characters in-universe have speculated to be akin to time-space manipulation or completely rejecting the reality of the event having ever happened.” Her only limit is her personality. If she believes that something is impossible, it doesn’t occur to her, or she doesn’t believe she can do something, she can’t. If Orihime didn’t have this limit she would be unstoppable.
Itachi would have won if he wanted to
After years of anticipation fans finally got the battle between brothers, Sasuke and Itachi. This fight was epic. The two battled in an intense standoff that sees Itachi gain the final upper hand when he uses his Susanoo. Suddenly, he touches Sasuke’s head just like he did in their childhood and dies. Itachi had been suffering from a terminal disease. However, he wanted Sasuke to win anyway. Tobi notes this, saying that if Itachi wanted to win, Sasuke would be dead.
Gohan’s broken arm
This is probably the most famous example of a drama saving handicap. After Gohan finally reaches SSJ 2, he dominates Cell. Nothing the villain could do harms the young Saiyan. Goku begs his son to end Cell, but the arrogance overcomes Gohan. After playing around with Cell, the embarrassed villain decides to blow up Earth. Goku sacrifices himself, dying to protect his home. Gohan finally realizes his error. However, due to his Saiyan cells, Cell returns stronger than ever. He kills Trunks and attempts to do the same to Vegeta. However, Gohan diving save keeps him alive. His arm is no longer any use. This results in the far more dramatic and entertaining Kamehame Ha clash, that Gohan wins with the help of his friends. Gohan wouldn’t have need aid if he wasn’t injured.
It’s cool when a mangaka finds a believable way to handicap a character to keep the drama and suspense- be it by putting some kind of “limit” on the character themselves or finding a way to keep them from the fight. Whenever I’ve tried to make a series; I end up making the protagonist too powerful and end up going back to square one. It’s why I read so many manga- I like to see different interpretations of this idea.
I think series like Demon Slayer and Jujutsu Kaisen are attempting to balance the power their main characters have compared to others and villains. It’s a difficult thing to accomplish.