When you first encounter her, of course she wants to "live until she burns up". But the more you progress the more she wants to live. Same as Gale who first just want to do something for himself whatever who is impacted, but then he carries about the others in the group and think about it longer. The moment Karlach has a piece of a solution, she wants to live, and ONLY IF there's no way to fix her, and at the very last moment, she will "accept" her fate to die. That's literally scripted in the game.
I mean we totally agree that she can have "bad" endings, that's the purpose of a RPG. If you fail something, you have to be prepared to have some bad news. But if you success, well you success, there's no reason not to save her if you do everything correct. She accepts to be a mindflayer if there's no other option. She accepts to die if there's no other option and you fail to convince her to live in Avernus. She accepts to go in the Avernus with you or Wyll if you try to convince her. Any of this is totally coherent. So why can't we find in all Baldur a very good blacksmith if we : - save everyone in Act 1 -save everyone in the forge - save everyone in the shadows ?
That's why her story doesn't give us a bittersweet ending as it was maybe intended as you suggest. Because everyone can escape their initial fate, all of them can have a long beautiful life, but not Karlach. That's not bittersweet, that's unfair, and unfair for no true reason. Especially when you have plenty of solutions in front of your nose while others like Lae'zel can be miraculous. Her queen has a Wish that she can use 100 times during the story to just kill her (and you can died like this if you pick some bad dialogue choices). That lets a feeling that Karlach story is unfinished.
Maybe my words are hard in my comment, but I never say Larian Studio are lazy people. And I don't mind if Karlach's story is not as developed or important as Lae'zel or Shadowheart quests. But please finish her story with the same storyline consistency as for the other characters. If she has to be the bittersweet character, so explain to the player why she can't be saved during the journey and what she have to do/fight to gets her freedom back as an epilogue. If it was not intended that Karlach have a bittersweet end, so give her a mean to be saved during the journey and let her have a good/happy end like the others.
We don't want a happy end to have a happy end. We want her the same in-game chances as other companions to be saved. That's all.
