"I don't think there's a way to fully punish you for that," Sam admits. "Not the way that you think you need to be punished. Besides, I think you do a very good job of that yourself." Which, yes, Sam can very much relate to. Nobody has ever punished him nearly as much as he punishes himself for the things he's done in his best.

Probably the closest had been Lucifer. Sam refuses to even consider those methods.

"And I don't know about Dean, but for me? My forgiveness was never only about what you had done to me. My forgiveness was...well, for all of it. Because I know that desperation, the one that eats at you and makes you do things you wouldn't because there's a hope, just a glimmer of one, that things will turn out better if you go that direction. Even when it turns out entirely wrong." Sam lays his hand on top of Castiel's head, almost in benediction. "If I can't forgive you for that hope, why would I ever deserve forgiveness for what I'd done for similar reasons? I wasn't lying when I said that I still thought you were one of us. In fact, I think that may have made you more of a Winchester than anything else could have."

They'd all three of them fucked up for hope. For the love of something larger than themselves. Maybe they didn't deserve the forgiveness, but they still had it, anyway.