"I don't have a choice." He hesitated. Always hesitating. It was what had gotten him killed; it was the same thing that had gotten Dean killed. Failure to do what was necessary. No, he wouldn't be the one to stumble and fall again. He had to be strong. Sam squared his shoulders and swallowed down the painful lump that had dug it's way into his throat.
"You're a killer," Sam said, slowly advancing toward her. "You killed all those people on the train. You've probably done even worse than that." He shook his head gently, looked down, and finally, after a brief moment of silent contemplation, raised his arm and began to focus on pushing her back. He'd pin her to the wall. It'd be over with soon.
He wasn't as strong as he could have been. Not without the blood. But he still had it in him.