I going to base my least-liked simply on play time, and going by that it's:
Least - Minsc! I get him just too late. Magic items have already been optimized, pairing combinations gelled, stories developed. Maybe in a play through I'll beeline to him Act3 before even Rivington.
2nd Least - Halsin. Act2, it's over. Sex pesting when MC is well into a relationship is not welcome. Plus he competes with Jaheira, who's actually a top 5 favourite. Guess I could respec him.
3rd Least - Karlach. On release I thought she'd be top romance pick, but found her simply unattractive. Doesn't help I prefer fighters over barbarians, and she's not very barbaric anyway.
Honourable mention - Minthara. Locked behind evil (for romance) or neutral path. I'd quite like her as a companion, but for me massacring the grove requires a certain MC with leaps of logic.
For Minthara I'm just roleplaying as the Durge who couldn't control themselves and led Minthara to the grove. They feel incredibly shit about it as they thought they were able to control themselves after killing Alfira, but the urge to slaughter was too strong. Afterwards they seek comfort in Minthara, probably another monster such as themselves. This is incredibly dumb on my part, but I have no other idea how to justify getting Minthara as a romance and getting the good ending.
If I didn't have to slaughter/ignore the grove I'd pick Minthara over Halsin every single time.
