The oldest being, archangel or leviathan?

Who's the older creature, Archangels or Leviathans? Older than normal angels, sure, but it's just very difficult for me to believe that they could actually be older than the archangels, I mean, they're archangels for crying out loud, the strongest things, besides God and Death. In my opinion, an archangel could annihilate a Leviathan. I'd love to hear your thoughts on this.