Ok, so I am not usually the vengeful type, but this has gone on too far. I was sexually assaulted a few months ago by my childhood best friend's husband, he lied about it, made me seem like I was crazy, and is spreading lies about me, and I am really fed up with it. My friend didn't believe me when I told her and she called me some nasty names, so I am looking for revenge. I have been a practicing witch for many years, but never felt the need to delve into the darker side of things. I am also 8 weeks pregnant, so I know I need to be careful with whatever I choose to do.
Aro, I'm not trying to be harsh, but you are not allowed on this site until you're thirteen. You're welcome to read about magick online before that, of course, but having an account is not the best idea.
The Old Mother Redcap curses suggested are both good ones if I'm remembering right.
You might also try something to draw attention to his actions and what he had said about you as compared to the truth. A lot of this is about what you want to happen to him, clarifying that would help a lot.