User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-29551856-20160408183239

Honestly, IMO, this is no contest. Archangel >>>...>>> Leviathan.

If Castiel was able to hold his own (a Seraph at that time), then Gabriel (the weakest Archangel) would curbstomp all Leviathans at once (Archangel >> All Seraphim combined). Considering that the weaknesses of angels rarely coincide with an Archangel's weakness, the Leviathans are most likely not able to negate any of their powers.

Also, the fact that the four of them contributed to defeating the Darkness is a feat in its own league.

The Leviathans get stomped.