Strongly agree on opinion about endless possibilities stored in DnD and game itself, that allows to perform miracles of all sorts. There are lots of hell iron in the game, but still no love for Karlach despite player's efforts. That is unsatisfactory: lots of ways to lose her but not a single to win. Personally I don't find
"return to Avernus"
ending as good one (only if somewhere player slighly failed in the process, but not gravely) - taking into account the fact that she loves this world and we, as players, may be spared for long time from ceremorphosis, travel to another planes, but unable to fix some tech while surrounded by lots of miracles and powerful entities. Unbelievable. So, I strongly hope that game is unfinished at the moment, and great Act 3 will be presented with endings, quests, and repaired our and Karlach hearts. JUSTICE FOR KARLACH! LOVE FOR KARLACH! P.S. Her death ending is not bad as it is (thoughtful at least), but this makes taste her overall quest line unfinished, not solid, and stimulating players dig all corners in attempt to save her. This, IMO, proves that good ending is a must have.
