Supernatural, Season 4

Sam:
You were in Hell, Dean. But maybe you did what you did there... but you're not them. They were barely human.

Dean:
No, you're right. I wasn't like them. I was worse. They were animals, Sam. Defending territory. Me? I did it for the sheer pleasure.

Sam:
What?

Dean:
I enjoyed it, Sam. They took me off the rack, and I tortured souls, and I liked it. All those years; all that pain. Finally getting to deal some out yourself... I didn't care who they put in front of me, because that-that pain I felt, it just slipped away. No matter how many people I save, I can't change that. I can't fill this hole. Not ever.