Dean and Sam in “Unfinished Business”

Dean

So what, you're just gonna walk back in, and we're gonna be the dynamic duo again?

Sam

Look, Dean, I can do this. I can. I'm gonna prove it to you.

Dean

Look, Sam, it doesn't matter. Whatever we do. I mean, it turns out that you and me, we're the, uh... the fire and the oil of the Armageddon. You know, on that basis alone, we should just pick a hemisphere. Stay away from each other for good.

Sam

Dean, it does not have to be like this, we can fight it.

Dean

Yeah, you're right, we can. But not together. We're not stronger when we're together, Sam. I think we're weaker. Because whatever we have between us; love, family, whatever it is; they are always gonna use it against us. And you know that. No, we're better off apart. We got a better chance of dodging Lucifer and Michael and this whole damn thing... if we just go our own ways.

Sam

Dean, don't do this.

Dean

Goodbye, Sam.