You can’t use your novel for revenge. Oh, it’s a fun idea, but it doesn’t work.
Sometimes I get this foolish idea to use a person from my real life in my novel, and if that person, you know, did me wrong, I think, “Aha! I shall make him evil or ugly or kill him off!” At least on the page I can vent my rage–at last.
Then I get into the character’s head and see things from his point of view, and–horror of horrors–I’ve got to be sympathetic. I try to twist him this and that, and yet he weasels away from me. The novel works better (right?), but I’m still pissed. Sigh.
Actually, I’m usually so giddy about the story I forget to be angry. I might even be–shhh!–grateful. So, use your enemies, but be warned; you might be the better for it.