The Time In-Between
He'd always hunted for his family.
But once your parents are dead, and your brother is the anti-christ why should he bother to fight it? Why doesn't he just give in to the evil.
If he did, it could stop. Sam promised him. If he just gives in to the evil, all the pain stops. No more beatings, no more being cut open and strangled nearly to death with his own intestines. He wants to, he wants to give in so bad; but not because its the easy way out.
He could have taken the easy way out a long time ago with a gun pointed to his head when his brother became evil..but he didn't.
--
He was lying on the floor, his own blood congealing around him, when Sam returned. It was one thing he could count on, Sam always came back. No matter how badly he'd beaten him, how close to death he'd brought him, Sam came back.
It was the coming back that saved him from giving in. Every time Sam came back he saw what he was.
Not Sam.
It was all him...except for the eyes. The demon in Sam had taken over and he didn't see the eyes that he looked into and promised to protect until forever.
That was why he didn't give in; because Winchesters don't give in to demons.
Because Sam was dead, but he couldn't kill the monster with Sam's face either, so he was just going to wait until it killed him.