User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-5120709-20120529162257/@comment-5120709-20120531222655

I think they go Mr. Buu, Grey Buu, Fat Buu, Kid Buu, Buff Buu, and Super Buu and all his forms.

Back to Supernatural, if I we go by how hard they are to fight maybe the Leviathan win. Both of them can be fought, but only by being cunning. With the Leviathan, when they fought Edgar and Chet they fought him straight on and got their butts kicked, but with Dick they played it smart and were able to kill him. With the Archangels Gabriel tried to fight Lucifer directly and died but Cas took Michael by surprise and scored a hit with his Assbutt Molotov.

The last thing is killing them. Both are hard, finding an Archangel Blade and the Bone of the Righteous Man, but the catch is what happens after you get them. You kill an Archangel and nothing happens to you, but when you kill a Leviathan you get sent to Purgatory