superhero whose power is being really good at diplomacy or something like that
That's a really good idea. It would be the superhero equivalent of a spreadsheet simulator game lol.
But I think a pretty important part of defining superheroes is by individualism, which is the bread and butter of Western culture. If there's not violence, there's still individualism. Like, think modern Sherlock Holmes. He doesn't commit a lot of violent acts, but he's still pretty much defined by being impossibly smart, almost to the point of having a "superpower".
The original Sherlock wasn't like this. Maybe I'm reaching, but maybe there was some influence from superhero stuff. He used to be an amazing detective, but had big gaps in his knowledge (like he didn't know the Earth revolved the Sun). Newer adaptations kind of make him a superhero in a sense.
I don't know if it's necessarily individualism that is the source of interesting stories or if it is cultural hegemony. I think it would be interesting to read some Marxist-inspired story where some group of workers build a party from the ground up.