I think the reason people like revenge is because they have been wronged and they want the wrongdoer to feel the same pain that was done to them. I totally get that! But I'm with you, doing something wrong to someone just to get them back is not really going to help the situation. If anything, it's just going to cause more problems.
They are lucky if they don't get caught. But they are screwed if they do. And like I said just a few minutes ago on another question, Nothing says "I'm not over it yet" like seeking out revenge. It just feeds the other person's ego and makes the other person feel justified in screwing them over initially.
in my opinion the best revenge is to be a better person. It's to work on oneself and try to live their life and reach goals.
It's not worth it to waste time and energy worrying about a person who didn't' care about them in the first place (which obviously was what was happening if they had no issue screwing the person over or hurting them initially)