Vengeance is a dish best served with roadkill, but you need a lot of foam kernels and a phat box.
I swear, one of the best indicators for whether someone is an asshole is an inability to mind their own fucking business. It's right up there with 'treats service employees like shit' and 'likes to torture animals' in terms of its predictive reliability. If you think you know someone well, and they get all up in somebody's shit where they have no business sticking their nose, it's time to re-evaluate that person.