User blog comment:EmpyreanSmoke/Weaknesses/@comment-3045936-20151001223032/@comment-5619706-20151002023724

Actually, your quotation only goes to show how "angels" are sometimes used as a catch-all phrase to include all types of angels, including archangels. It is canon (unless retconned in Season 11) that the Leviathans were the first creations of God. So "angels" in this context will include even the four most powerful angels--archangels, but angels nonetheless. And since this context extends to the next few lines that Leviathans could chomp off the petri dish, it actually serves as one of the bases why people think Leviathan can consume archangels.

However, I, for one, am not a big fan of all this edit wars. General rule is we post only verifiable and canon weaknesses of beings/characters. Deduction is okay if sources and citations are both credible and plentiful. For this topic, there are canon statements to support it, but also a lot of confusion due to contradictory scenes (why is Castiel sometimes able to use his powers against Leviathans?).

What we know for sure is that ONLY the Bone can truly kill a Leviathan. Scythe of Death is highly possible, and God, as well. Everything else are conjectural and at best can only incapacitate a Leviathan unless expanded on the series.

But can Leviathans eat archangels? Canon statements exist and support the idea. Can they do it effortlessly? That may be another matter entirely. Remember this show has pagan gods, angels and monsters being killed by mere humans.