So there's a good example of this type of character and its found in one of the most popular anime with one of the most popular characters, <PERSON>.
<PERSON> is the teacher in Jujutsu Kaisen. He helped the MC to accomplish many goals and be stronger. If I can describe <PERSON> in a few words it would be 'overconfident and overpowered upside down <PERSON>'. He's handsome, he's smart, he's the strongest Sorcerer alive according to himself and other characters within the story. And he proves his strength to one of the antagonist, to which he didn't break a sweat. However he does have a few weaknesses; his attitude (especially to old people); his overconfidence, and his emotions.
So basically spoilers: He may be perfect, but it doesn't mean he didn't do mistakes. (1) He didn't manage to accomplish one of his missions that caused his best friend to spiral down to madness. Then his best friend came back to do his grand plan of his ideal view of sorcerers and non-sorcerers. After his (former) best friend was defeated, (2) he didn't dispose his corpse; Which then allow one of the antagonist of the series, to use the body as a host. (3)Then he got sealed in a box, as he failed to escape; because of the person who used his best friend's body as a host, gave him time to be frozen in place by his emotions.
All those points there I put, is to pin point his mistakes, that affect the plot. And eventually lead to his downfall, of being sealed in a box. 86
So <PERSON> is strong but he has weaknesses. That. They must have a weakness or they didn't manage to succeed, all their endeavors. And his best friend once defy him. <PERSON>'s weakness of having emotions of his best friend; and not disposing the body, was his mistake that put him in the box. And over the course of the story, his character arc develops him of being strong but not the toughest. His emotions lead him wanting to be a teacher and make a better world through his students; but its also a weakness as, I've said it before, his only friend.
they even did this other trope of him gaining a power up, but it wasn't enough to defeat his enemy, and he still fail his mission. <PERSON> didn't understand how to use that skill but after he does, he still fail.
Give characters flaw and use that as a disadvantage to them and proves them human. Use their flaw or loss to progress or affect the plot. And show them struggle, how did they become OP? is it because of their hard work and endeavors? or is it because they're talented?
That is a way by <PERSON> to prove that OP characters can be not so OP. Hope this helps. 190