except for Zapp Branigan. I couldn’t stand that bastard.

Yeah, but as a story writer and worldbuilder I’m inclined to cut them some slack on Zapp. I’d say writing a balanced and well thought out morally-bad character or villain is the hardest thing in character development. Counterintuitively, you can’t make the reader genuinely hate them like many do with Zapp, even if they are the designated big baddie, because if they feel such strong negative emotions, they won’t want to keep reading/watching your story. The reader doesn’t have to agree with their ideology or actions, there is a misconception that the villain always needs to be a little right to be compelling, but that’s not necessarily true. Really the most important thing is you need to make sure that you’re not making a character that the reader can’t stand and reading their interactions an unpleasant experience. At the same time, you have to make their motives believable and make them evil enough that whatever punishment your plot has in store for them is actually justified, all while still retaining a basic level of sympathy in the reader. I feel that Mary Sue heroes are talked about way more, but Mary Sue villains are just as detrimental. I definitely struggle with this.