I start yelling oww and acting hurt. If the cat is grown, but not super violent, I'll scream oww in an annoying tone and shove the spot they bit or scratched into their face for a few seconds. Then I'll do it again a few seconds later. It probably sounds crazy, but I've raised multiple cats, and one of my friends said the one we adopted from her is a lot less violent and mean now.

One of the cats likes to be on our shoulders, but she knows she's not supposed to jump up there unless we have a shirt on.