"I'm good with who you are."
When Dean says these words, Sam's first instinct is to break down sobbing from relief.
He's been afraid of this for years: that his brother loved the old Sam, the old Sammy who was young, and pure, and relatively innocent (he'd never quite been innocent).
He knew Dean loved the old Sam, even when he broke the final Seal, even when he drank that demon blood, because he was still his Sammy.
But Sammy died years ago, died as soon as he jumped into the Cage carrying two Archangels in tow.
He died as the Archangels beat and tortured him in horrific ways, as Lucifer raped him and buried his fist in his soul, twisting and tearing, but never destroying. Just breaking.
And Sam was so, impossibly broken. Broken in more ways than Dean knew, because he'd always been so afraid to confess this, even if Dean did know, and Sam suspected he did.
But that's part of why he's been so afraid to tell Dean what all happened down there in Hell; he's always been so scared that his brother will only look at him with pity and disgust, that he's only been clinging to the remnants of Sammy and that he doesn't care for Sam as he is.
Sammy was frozen cold by Lucifer as the Morningstar wore his flesh and controlled his mind, stifling and stealing from the soul within.
And then he was burnt alive in Hell, ripped apart by meathooks, raped, soulfisted, and then frozen all over again.
There's only a few shattered fragments remaining of Sammy within Sam, a few fleeting memories Lucifer hadn't quite tarnished as he'd picked apart Sam's brain and spoiled most of his good memories.
But in truth, Sammy had always been dying.
He's been dying since the day he turned six months old, and then again when he learnt the truth about their lives, and again when Jess died, and when Ruby betrayed him, and again and again and again. Lucifer has only expedited the process.
Sam is consciously aware that the body he wears is a corpse; it isn't his. It has never been his. And it never will be his. He's been violated in too many ways for his body to be his; possessed, raped, killed, fed demon blood...
There's barely anything left of Sammy, but Sam carries the fragments proudly. He laughs when Dean talks about their old haunts, even though it takes great and painful effort to even remember some of them. Usually Lucifer is there too, as he's taken care to insert himself into practically every significant or even minor memory of Sam's life.
That's why Sam doesn't like to dwell on the past, that's why he's been focused on making sure Sammy and all of his past mistakes remain dead. But he knows Dean wants Sammy.
He didn't think he wanted Sam.
"I'm good with who you are."
Sammy is screaming inside of him, begging Dean to take it back. Because he's not okay with who he is; he hates it.
He desperately wants to go back to the way they were, when they were equals, or at least more equal than they were now, before Lucifer ruined him, before the Trials, before Purgatory, before Gadreel, before the Mark, before the Cage, before he'd jumped in with two Archangels in tow.
He's not as dead as Sam thinks he is, and he's crouching inside, waiting for any opportunity he can take.
But it's stifling in here, and it's hard to overpower Lucifer's icy influence on his mind. He wants to be free, he wants to leave.
But he's been broken down, beaten down. Mostly by Lucifer, but by Dean too.
Because doesn't want Sammy back. And Sammy realizes this now. He thinks he's stupid for not realizing it years ago, when Dean started tearing him to shreds for any little mistake he made.
When he blamed him for things that weren't his fault, even before the Cage. When he blamed him for losing his soul, for not looking for him in Purgatory, and for stuffing an angel inside of him against his will, and for saying he should've died when he had the chance to.
Sammy finally realizes that Dean doesn't want him, and maybe he never did; he's been working his whole life to stifle him, to slowly destroy him, even if he didn't realize it.
He never wanted Sammy. He wanted Sam.
And despite all the years of hanging by a thread by Lucifer, of remaining dormant within Sam Winchester's broken mind, Sammy finally takes his dying breath.
Sam doesn't notice; after all, he thought Sammy had died long ago.