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.
It’s very hard to say, if they kill any character in my opinion will be right at the end of the game as I’m sure they want to keep selling banners.
I have a feeling that the abyss sibling is already dead/will die like we are trapped in a cycle and all of this happened already.
I’m also think that not all archons will be playable and we will see a replacement show up, a new archon.
But idk that’s just me and my theories.