Mary-sues, bAD sp3LLahz, pop music, bullies, racists, sexists, nationalists, homophobes, jealous people, spammers, trolls, being a drone/a clone/a mindless sheep/a trend follower. Etc.
Funny, I'm opposite of you, I hate teenagers (at least the immature ones, but some are pretty nice, it's just I don't care that Sally was dating Tommy but then she slept with Jimmy.)