"He is," Peter said. "And I couldn't. The man he is now, the one that lives here, is not the man I hate. That man is lost in time, and the man I see struggles every day with the knowledge of what he might become. He doesn't want it. He would rather die."
At the look from Jacen, Peter dropped his gaze. "I made that choice once. Be the monster, save the world. It destroyed me. I'd like to think that the circumstances were the same now, and I was making the other choice, but it's not the same. Being here, makes it a thousand was different. Here, I can't be the monster. I can't lose it all again. There's more at stake than just my own happiness - my family, my friends, all the people I care about... they need me as much as I need them. It wouldn't just destroy me. If that was the case, I would do it. But it's more."
He let out a breath. "I let him live. And let him know that the moment I stop seeing Gabriel, the moment that Sylar is the man he's become, that he wouldn't survive to draw another breath."