The Moment
It wasn't the blood.
It wasn't the killing.
It wasn't even the black of his eyes.
It was the moment Dean stood over him, blade in hand, about to deliver the killing blow. It was the moment he started to smile, and then threw his head back and laughed, laughed like he hadn't in years, laughed like he was happy and finally free.
It was the moment Sam looked up at his brother and realised.
In all the time they had known each other, from the moment Sam was born, there had never been a single moment when Dean had not cared about his little brother. Dean's first priority was always looking out for Sam, taking care of him, protecting him. Through every hardship they had ever faced, through all the fights and the lies and the betrayals, through Heaven and Hell and everything in between, the bond of brothers might have splintered and frayed but it never broke. There were times Sam may have felt rejected, hurt or abandoned, times he thought they would never be okay, but the truth was that Dean never stopped loving him.
Sam never realised how much he had taken Dean's love for granted until the moment when he looked deep into his brother's eyes and saw that it was gone.
That was the moment he knew.
Dean Winchester was dead.
And the monster wearing his face was going to kill Sam in cold blood. No hesitation, no regrets. He was going to enjoy it.
Sam wasn't afraid to die. He had already lost everything.
He had lost his brother.
Sam closed his eyes, Dean's laughter ringing in his ears.
It was the last thing he heard.