Don't tell Sam this, but Dean can't hate him, never could, and only blames him for one thing, and it's none of the big ones, none of the obvious ones—Sam trusted Ruby to save Dean, Dean trusted the crossroads demon to save Sam; Sam let Ruby break him down and rebuild him how it suited her, Dean let Alistair slice him apart and sew him together in his image; Sam freed Lucifer when everything he knew said he was preventing exactly that, Dean doomed Mary and condemned Sam when everything he knew said he was saving them both. Better if Sam believes Dean hated him, might still hate him, for that, because that might actually be effective where watching Dean make those exact mistakes wasn't—big brothers exist to make mistakes for their little brothers to learn from, and sometime when Sam was a teenager, he stopped thinking there was anything Dean could teach him. That's the one thing Dean can never forgive him for; that's the one thing—they have to be brothers and equals, not brother-mother and brother-son—that can never be the same again.