I'm surprised no-one has mentioned Captain Phillipa Louvois, the JAG officer from Measure of a Man, who said she would summarily rule against Data if Riker didn't act as prosecutor in her sham trial. So if Riker screws up or wimps out Data suffers? In what universe is that
On the other hand, I loved Shelby and wished she'd been in more episodes. She had great chemistry with Riker and gave him a taste of his own attitude. They were entertaining together.
I agree that Jellico wasn't really a terrible captain, but he was doomed to be hated by most fans simply because Picard is loved, so anyone who tried to replace him was going to be hated, whether they were really a jerk or not. And Riker and Jellico were a bad pairing for leads, at least on any kind of long-term basis.
The biggest jerk in TNG was Dr. Polaski, though. Her disrespect for Data was the most painfully obvious, but she was patronizing and disrespectful to everyone, and downright rude to her own nurses and assistants in several episodes. And, unlike Maddox, she never seemed to learn that she was being a closed-minded, prejudiced jerk. Ugh. She actually rendered several episodes unwatchable for me, because I'm so busy hating her I can't focus on the plot.
I'm not sure Maddox should've been counted as a jerk, because he's an antagonist
, the character intended by the writers to be the driving force of conflict in the episode. If we're going to count Maddox as a jerk, then we need to count every villain from every episode, and it's going to become a very long list indeed. I usually reserve jerk status for the characters the writers cast as protagonists who I none-the-less wanted to see murdered horribly by the end of the show.