Superheroes can have flaws, "kryptonite" is practically a commonplace term for "a significant weakness". They can have weak points, flaws, they can make errors. But I must draw upon Anime to make a point. Specifically, Fate/ZERO. On the speech Iskander makes on the concept of being a King.

The king must be greedier than any other. He must laugh more loudly and rage for longer. He must exemplify the extreme of all things, good and evil. That is why his retainers envy and adore him. And why the flames of aspiration, to be as the king is, can burn within his people.

This applies to Heroes in general. A Hero isn't someone paid to save people. A Hero isn't even someone who saves people out of the goodness of their heart when presented with the opportunity to do so. A Hero is a Greater Person. Not a great person, greater. They are defined from tabula rasa as "more than".

Superman is Faster than a speeding bullet, stronger than a locomotive. But morally, too, he is gooder. By definition, a Hero cannot be reached. They embody what the feminists call "unrealistic portrayal" of humans. The most we can do is aspire to approach them. Villains, too, are Greater Persons. More evil, more cunning, even in some cases more petty than any human could aspire to, showcasing the worst, something to shy from.

That is the baseline of a Greater Person, they are beyond us in some unreachable way, but which either draws or repels us in that aspect. Real World Examples: If you say "I want to be like Nikola Tesla", you probably mean "I want to be creative, insightful, and intelligent", not "I want to be a dying-young virgin with only feral pigeons for friends". And on villainy, if you don't want to be like Hitler, you're probably thinking of the systematic murder of millions, not his belief that recycling is important for long-term societal stability. (At least, I hope you aren't viciously throwing a coke can into a compost bin with a knowing smile that you won't support Hitler's recycling ideals, but are fine with the other one.) In writing, likewise, there is infinite room for creativity in those secondary aspects and building the character, but line one of their description should be that Greater aspect that one must wish to approach, or fear.

But this is antithesis to modern western writing, where everyone must be "human". They focus on the flaws and lesser aspects. No one wants to read a story about Batman's struggles with changes to the tax code. He obviously deals with them, it's implicitly known by all of us, but no one cares, it's not his Greater aspect: World's Greatest Detective.