A Psychopomp. Think... God's postal service. They get the souls of the dead where they're going, and protect them from anything along the way.

Even the strongest of beings doesn't wanna mess with a Psychopomp. Archdevils, Archangels, Avatars... it doesn't matter. They're basically gods themselves, except their only concern is seeing the souls of the dead safely on their way to whatever comes next.

Um.... The Grim Reaper, for example? Psychopomp. Charon? Psychopomp. Death? Aurora? The Valkyries? Psychopomps, all.