Call him "committed."
Seriously, it is a waste of time to devote the energy necessary to come up with a derogatory label for someone you don't like because he hurt your feelings. The question appears to be seeking an avenue for vengeance, and vengeance serves no purpose; there is rarely any satisfaction gained from it, and it only feeds on itself.
If you are still looking for the best of the worst names you can call a guy, call him nothing. Literally say nothing to him. Isolating him from your life will hurt him more than if you dropped a two ton car on him from two stories up. Shun him.
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WikiAnswers takes a dim view of cyberbullying, or bullying of any kind for that matter. Seeking derogatory or pejorative names to call a guy is sort of like that bullying thing WikiAnswers does not like. Keep that in mind when adding answers here.
Names that describe specific behaviors: