User blog comment:EmpyreanSmoke/Supernatural Q&A/@comment-168.169.25.92-20150924215559

Are Knights Of Hell really stronger than archangels? I mean no disrespect but archangels are severely underrated in this wikia. It's stated Knights Of Hells can kill archangels, though no proof supports this. Lucifer ( an arch angel) created the Knights of hell. Also Abaddon retreated at the sight of a normal angel. (Who was severely weakened at the time) Knights of hells aren't even stronger than white eyed demons or yellow eyed imo.

Also their is no proof that archangels can be killed by leviathan. Castiel, a Seraph. Was able to hold his own against two low ranking Leviathan in Purgatory. Raphael (an Archangel) effortlessly beat Castiel and would have most definitely killed him if Balthazar hadn't intervened. Castiel was also empowered with 50,000 hell souls on top of being a Seraphim. Furthermore, Castiel powered with 30-40 millions of souls and Leviathan, although easily obliterated Raphael, was still scared of releasing Michael and Lucifer from the cage. This suggests even the highest Leviathans are completely no match for the Archangels. Or at the very least Michael and Lucifer. I borrowed this. Again no disrespect