User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-98.113.182.208-20120512155723/@comment-184.77.255.73-20120518201748

Uh, Michael.

He's older and more powerful than even Lucifer.

Dean wanted to use him to "ice" Luc, but they would've had no way of getting rid of him afterwards.

I agree with the rest of your post, though.