User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-5110811-20150606161023/@comment-3045936-20150606195325

As far as if the Archangels are able to negate the Leviathans ability to be immune to Angelic power. Idk, at this time. The only conjecture I can offer is this. Numerous ones were in Castiel and he had 40 million souls making him at least as powerful as Michael to more likely stronger. And they still were making his vessal break down.