I always hated Donna the most. If they were going for a "stupid melodramatic teen" with her, then boy did they hit the nail on the head. And you knew that when Donna goes on an investigation, it's gonna end up with someone dead or in a hospital (the orchids dude, the psychiatrist,
).
But James is a close second. Very punchable.
I thought they gave up on that plot because they realized a grown man banging a high schooler was not exactly a good idea for romance, particularly for a character like Coop.
Then again, Nadine subplot. I guess it's OK as long as the roles are reversed? :|