In my opinion, I think it’s gonna be one if not all of the Archons that took part in Khaenri’ah’s destruction by sacrificing themselves or something similar to atone for what they did. Even if they did it for the greater good, a lot of people still died by their hands so they probably feel guilty.
Or Childe, I mean look at his eyes, the dude’s already dead inside.
Albedo’s event quest hint at a potentially bad ending. Meanwhile, Lisa and Baizhu are running out of time, so…
Also, as much as i don’t want it to happen, having either Beidou or Ningguang die will be an incredible gut punch.