"edgy" is a reasonable definition of a trait but it's not always bad. as long as the character has an arguably justifiable reason and mean to break away from society's mores there is nothing really artistically wrong with it.
the reason why it is defamed is two-pronged: some of it is that people instinctively are repelled from discarded aspects of themselves or others (ie, they had a phase when they were growing up in a sheltered middle class life where they skirted close to dylan and klebold) the second prong is that dissidents and outsiders scare them on a physical/emotional level, as rebels to society can be physically and emotionally dangerous.
tl;dr, edgy is fine, unless it's self-insertion or the character does not have a reasonable (or unreasonable) reason for being the way they are.
people have a weird tendency to believe that every character somehow reflects the author, but realistically it is very possible to write characters that do things that are not justified, and that is not necessarily some sort of justification for similar behavior in real life. You see this often with SJW types where the fact that a certain character exists in a certain way offends them, even if they are supposed to be a bad guy.
