lmaoooo this question... is it cheating to say traveler? i get the sense they won't stay in the world forever anyway, so maybe they sacrifice their life to help preserve the people of teyvat.
if i can't pick traveler, it's tough. i love all the characters, and the ones i care about least are so insignificant to the plot that i can't really imagine a satisfying way for them to die.
OH WAIT aloy! no offense, but i honestly forget she exists most of the time.