User blog comment:ImperiexSeed/The oldest being, archangel or leviathan?/@comment-166.248.69.2-20110928165247

It's stated that god created these beasts before angels. Castiel is no pushover and granted he was in a weakens state he died in 5 seconds. They are clever beasts. I think if Michael had his sword he could win. Otherwise no. Death seems to be the only creature currently accessible. Kind of. That can kill a leviathan easily