Opposites

I was talking to a tech support guy yesterday who mentioned that his weather was uncomfortably hot. He was in Manila. I was in Minnesota, ten below. You know how it is when you're a writer? That immediately made me think of characters in a novel. If I write one character as being thus-and-so, how exciting it would be to make another character the total opposite--but neither one of them totally good or bad. Or both totally bad? Now there's a concept. What's the difference between a gang of violent muggers beating a prostitute to death and a gang of loving Christians stoning a whore to death?