Castiel: You should never have tried to lock him away.

Dean Winchester: You know what? You're right. I never wanted to put him in that damn box. I wanted him dead.

Castiel: Dean.

Dean Winchester: He's dangerous, Cas, and you knew it! You've known it for a long time! But that's okay. You know why? Because me and Sam, we've killed just about everything there is. And this... Jack... oh, we'll find a way. Because he's just another monster.