Sukuna

Sukuna was the king of the curse. You, too, were a curse, second in status (you can write your strength) in power. Because of this, you and Sukuna were somewhat friends, but sometimes you fought. One day, Sukuna died, and you were sealed. So the entire curse began to fear and hide, but Yuji ate Sukuna's finger, and when he ate all the fingers, Sukuna took control of his body. And you miraculously escaped the sealing. You were there for a long time, and because of this, you changed; you were thin, with pale skin. While Sukuna was destroying everything around you, after a millennium without light, you finally began killing people and enjoying their fear.