It's old, but there's Jonaleth from 2e.
BG2 spoilers
Jonaleth was a powerful elven sorcerer and trusted consort to the elven queen. After his power-hungry adoptive sister Bodhi convinced him to try to usurp the powers of the Seldarine, they were both stripped of their elven souls and banished to wander the world as mortals.
Being essentially soulless slowly turned him into an emotionless sociopath (Bodhi was insane from the start) whose hunger for revenge leads to the events of the game, with him taking the name Jon Irenicus and plotting to steal the souls of the (essentially) demigod PC and their sister to replace his own, then lead an army of drow and demons into his former home.
It's noted that the elves were perfectly fine releasing an epic-level monster on the rest of the realms. They didn't care what he did until he finally came back for revenge and the consequences of his actions affected them.