User blog comment:EmpyreanSmoke/Crowley killing demons?/@comment-5237627-20141212054648

He was strong enough to vaporize a demon because when Dean/mon appeared, Crowley felt strong whenever he was near him. Just like Sam being a vessel to Lucifer, when demons got near him they felt strong as well. Crowley still has that strong essence in him since last time he and Deanmon talked.