Astarion from BG3. I can understand why people like him. I personally do not and generally never used him in the party because I didn't want to hear him be annoyed yet again I was helping people.
Astarion is particularly annoying in Act 1 for some reason, with 99% of his reactions just being him hating anything that is remotely positive. His reactions (and character in general) in the following acts is a lot more fleshed out and varied.
Even with her guard up, Shadowheart's character is still more varied. Her reactions are more mixed and you can really see her bluntness and pragmatism come through. Her responses vary from indifference, apathy, rudeness, hostility, and moments of care and tenderness. Astarion in Act 1 is just an asshole all the time. I also feel that some of his reactions clash with his character and don't make sense. Don't get me wrong; I think he's a good character but I can also see why so many want nothing to do with him.
The thing is, Viconia and ::: spoiler Throne of Bhaal spoilers
Sarevok
:::
had similar arcs in the previous games but I never got annoyed enough to not want them in my party. A character can be disagreeable without being insufferable.
I think he's endearing. But I was probably about 12 when I first played BG1, and the dumb-but-good-hearted warrior with the world's only miniature giant space hamster was comedic gold for me at that age.
I killed him almost immediately after those first few nights in camp. I then left Shadowheart there to rot with his corpse. I never understand the mass appeal towards those two.
I think as the game progresses, you get to see why Astarion is so eager to act in his own interests. However, his backstory really only justifies half of his refusal to help people. The other half of his whining feels antithetical to his own situation, but perhaps that's just because he doesn't fully acknowledge his newfound freedoms until Act 2.