Good point about the necessity. Sometimes they can be necessary - a good antagonist causes conflict and gives characters something to strive against - but if the bitchiness is contrived or doesn't really add anything, it's worthless. The Ambassador Gamble thing fell into that.
The D/C AU I mentioned also fell into that, with the characterization of Jo. She was randomly written as abusive, annoying, possessive, overly jealous, and controlling, not to mention capable of sexual assault. It came across as incredibly contrived because all Cas had to do was say "thanks but I'm not interested in you" but for some reason, he never thought to do so. Thus, 40K words of a convoluted plot where Cas cheated on her with Dean but this was somehow romantic and a good thing, as Jo's characterization grew progressively more paranoid and OTT. The whole plot was pointless because there was no need for her to be in a relationship with Castiel to begin with and I don't think it ever addressed the fact that yes, she was paranoid, but she was right to be considering that her boyfriend was cheating on her with her best friend.
Re: Questions about character bashing
Good point about the necessity. Sometimes they can be necessary - a good antagonist causes conflict and gives characters something to strive against - but if the bitchiness is contrived or doesn't really add anything, it's worthless. The Ambassador Gamble thing fell into that.
The D/C AU I mentioned also fell into that, with the characterization of Jo. She was randomly written as abusive, annoying, possessive, overly jealous, and controlling, not to mention capable of sexual assault. It came across as incredibly contrived because all Cas had to do was say "thanks but I'm not interested in you" but for some reason, he never thought to do so. Thus, 40K words of a convoluted plot where Cas cheated on her with Dean but this was somehow romantic and a good thing, as Jo's characterization grew progressively more paranoid and OTT. The whole plot was pointless because there was no need for her to be in a relationship with Castiel to begin with and I don't think it ever addressed the fact that yes, she was paranoid, but she was right to be considering that her boyfriend was cheating on her with her best friend.