Naruto: Shippūden

Kankuro:
Sasori. Your strength came because of your soul, not in spite of it. You tried to erase it, to become a puppet yourself, but you couldn't change completely. I know this because you put your heart and soul into the puppets you created. That's the part of them that never decays. Now you've got your immortal body, but you've fallen, sunk to the level of the puppets you used to control. You were supposed to be a top-class ninja puppeteer, not a worthless nobody who lets someone else pull the strings!