Ryan Howard from the Office springs to mind. I guess his rise and fall was interesting but anything before and after that? Never seemed to know what to do with him. Always seemed weird that he was in the opening credits alongside Michael, Dwight, Pam, Jim and later Andy. When he never seemed anywhere near as important as them. Hell his weird girlfriend stood out more than him, and she wasn't all that great either.
I think they screwed up from the begining setting him up as the straight man, when characters like Stanly and Jim do that infinitely better.