Astarion: It should come as no surprise that I really like Astarion! I tend to gravitate to characters that are unlikely-likeable, usually due to their eccentricities and quirks rather than charm - and Astarion fits that bill perfectly. He's not my type at all (in fact, the first time I saw him, I just kind of rolled my eyes) so his writing had do the heavy lifting in winning me over, and it did!
I think that there is an excess of sexuality but absence of substantial inclusions of the same in most games - sex is either embodied by characters and serves as eye-candy, or it is inherently exploitative (throw-away sex-worker NPCs; the threat of sexual violence over side characters or the player; the quintessential perverted, ugly, violent cast-member with a receding hairline and the filthy sweatpans) but seldom do I see sex discussed and talked about in ways adults do. There is a lot of that with Astarion - his character's sexual predilections aren't just there to progress your relationship or to allure, they are actually spoken about frankly: the good, the bad, and the π€·. I found that to really stand out in his writing; as someone who laments the almost strictly unserious way we talk about intimacy in the modern day. This is what's kept me hooked all this time, I think.
Besides that, of course, his character is extremely funny and well-rounded, and his quest doesn't only lead to an incredibly satisfying conclusion but it's a rather fresh take on a vampire story - which is fantasy trope that used to bore me to tears. I have given the rest of the spawn so much thought and importance in shaping who Astarion eventually came to be, you have no idea, lol.
Karlach: Another character that I'd say got done a little dirty, not as much as Wyll by a mile, but I certainly still feel like a lot got left on the cutting-room floor with Karlach. I wasn't necessarily expecting for a cure to her affliction by the end of the game (In fact, I kind of wish that her death was non-avoidable) but opportunities seem to have been missed at truly exhausting the possibilities. While all of Karlach's dialogue about her situation hit HARD and feel incredibly real, the actual events that lead up to them lack a little gravitas, in my opinion.
That all being said, I really like Karlach. She is a wonderful subversion on the "dumb barbarian" trope - not because she's book-smart and poised, but because she actually displays a lot of emotional intelligence and skill in introspection. Karlach is an example of someone that can be kind, rambunctious, and willing to give people the benefit of the doubt without being naive - though perhaps that is something she had to learn the hard way.
Halsin: This may be my shortest input yet - but I just don't find Halsin very interesting. There is nothing wrong with his character, he's just kind of a good guy who largely seems to have already done the emotional labor that the rest of the party is working towards - he's funny, and his uncontained yet "polite" brand of horny pursuit is novel, but he just isn't my type of character π
Jaheira: HER, on the other hand -
Jaheira presents a lot more flaws that I can latch onto. She has her own, mutating idea of justice and morality and her own exceptions to the same - she's a questionable mother who just seems to pick up strays off the side of the road and then leave the door open in the hopes they will feed themselves. She drugs you immediately upon meeting you like a lunatic and is proud about it. Her banter is phenomenal and I love how she plays along if you make fun of her. When will someone make a Jaheira Romance mod....
Minthara: I love Minthara's fish-out-of-water perspective a lot - she is not a "good" drow or a rebel to Lolth (not willingly, anyways) but someone who has already fully matured in their culture and thrived in it, enough so that they understand how different it is to that of others - her willingness to participate in top-side affairs while casually commentating in its strangeness is hilarious to me. Her pragmatism is hilarious to me. In no small part because it brings a lot of realism to the world that was previously missing to me- the idea that cultures of SUCH extremes can still respect each other and cohabitate, especially when they find themselves in each other's territory is... Fascinatingly human, LOL.
She also has some of the most interesting dialogue, in my opinion. Her introspections about her own actions and of each of the companions are shockingly objective, and she might be the only companion to have made me strongly reflect on IRL behaviors of mine.
Minsc: Joey from Friends but funnier.