I think wanting to take revenge on some one, just proves that you didn't really feel that much for them. 'Tis far better to pity them. The fact they have to hop from one relationship to another, without being honest and direct, sort of says it all, as far as i can see.
Move on! It is their loss after-all and life really is too short to spend it in a relationship where just one of you is fulfilled. There are plenty of others who want to love and be loved by you. Just go out and find them