User blog comment:EmpyreanSmoke/Supernatural Q&A/@comment-79.115.75.190-20150922191935/@comment-26992577-20150922192501

Was already answered 4 pages earlier.:

Q: " Could the first blade kill Death? or Michael? the leviathans?"

A: "I'm not sure whether or not it could kill death (as the darkness is still a mystery), but it could kill Archangels and Leviathan."