Let's say your friend owes you a hundred bucks, but he's always saying he'll pay you next week. Now you want to do something to hurt him, but you still want him to be your friend. This could work. Go to your friend's apartment with a brick and knock him out with it. Then, set his apartment on fire. When he comes to, be standing on his burning couch dressed in a red jump suit with pointy-ears and a pointy-tail. And be holding a pitchfork if you can find one. Then say "Give me one hundred dollars and I'll set you free." But don't accept a check from him. He is a deadbeat, after all.