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.
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:
Meg is not the worst name in the world. Many associate it with being a bad name choice because of the character on the television series "Family Guy" with the same name.
By his name.
Worst case of suicide He had ever seen
The superhero Marty draws in "The Worst Thing About My Sister" is called Super Guy.
yes in Canada's worst driver season 6 it happend (guy removed other guy's insurance
A sausage roll!!
There name, or nickname if they have one.
Lizeth a guy and gabby a guy
se7en
No. Colt use to call it "my truck"
his name was Levi
They're race slur name