I think that Colin was definitely a jerk before the accident. Sweet/Charming when he needed to be but definitely jerky. I'm not sure he was a "bully" per say, even though Bright sort of was, I can imagine Colin being the ringleader and Bright doing the dirty work. Colin probably didn't waste his time with people that were beneath him.
Post accident I think Colin was a pretty nice guy. I think he was just so confused because of everything people were telling him and obviously frustrated because of the memory loss and trying to live up to peoples expectations, and he was still recovering from the coma. Unfortunately, he started to go downhill because of his injuries and didn't get the chance to grow and develop into a new/better person. Which is really sad.
