However not every story needs, or should have the wines and roses happy endings.
Karlach going back to Avernus with Wyll and Tav seems actually happy to be there. The cigar scene to me is awesome. She can stay in the Realms but would have to accept being a Mind Flayer. While this might not be the life she desires it is a choice to live and then of course she can choose death.
I get that everyone wants every ending to be all smiles and giggles but the ending for Karlach, to me is not nearly as bad as people are making it. She has the chance to have two dear companions adventure with her and help her enjoy sweet revenge on those that hurt her. That seems a pretty good way to go forward in life to me.
