Russell Quitman is, to put it simply, a meathead and a jerk. He's a big dude at school who likes to pick on people who are weaker than him. This already makes him despicable to Cullen, but what really makes him Cullen's nemesis is the fact that Russell is dating the unobtainable Ada Taylor. As Cullen understandably asks:
How is it that Russell Quitman, the Quit Man, could be so cruel, such a huge douche bag, and still manage to go out with the prettiest girl in town? (1.19)
Cullen finds this whole situation quite unfair and spends a lot of his time wishing terrible fates on Russell… until Russell actually does meet a terrible fate. He ends up in a car crash and is paralyzed, at which point Cullen can only feel sorry for him. He can't even hate Russell again once Ada goes back to him after briefly dating Cullen. It's clear that Russell is also a victim in this whole scenario.
Which leaves us with just one question: What do you make of Russell's last name?