I never liked the ending of Overhaul’s arc. Not that he wasn’t a bastard or that the writing was wrong or anything, I just don’t enjoy watching villains suffer like that.
It always feels somewhat gross. Like, we’re meant to get some kind of catharsis out of watching him be tormented, but since you can’t have the heroes do it without them being amoral scum you let a villain handle it instead. It’s like a form of sadism for the audience.
It does play into Tomura’s overall character growth, but I’m fairly sure you’re not supposed to feel sorry for Overhaul.