Ignore is worst. When you are avoiding somene, you try to go around them and not converse with them. Yes, sometimes you get caught and have to speak with them when need be, so they stil believe you are friends. However, when ignoring someone, you cut them off completely. Even if you see them, you just continue on as if they are nothing. Here they know that something is wrong and that you aren't friends. It's psychological bullying from my perspective.