Originally posted by TricksterPriest
Presence, Mikey, maybe Lucy. It's a short list. He may not even be killable. Hell, wasn't one of his origins possibly Cain before they revealed that was Vandal Savage?
IIRC, his possible origins include:
-Wandering Jew story
-A fallen angel who was neutral during the war in heaven.
-Survivor of previous universe similar to Galan/Galactus
-Someone who committed suicide after questioning God's actions after he was spared God's wrath initially.
Spectre and Nekron were unable to do it, but I'd partally attribute that to the fact that he has some level of protection/damnation by the Presence (3/4 of his origins involve this, and the fallen angel story is kinda confirmed by Constantine in Trenchcoat brigade), so at least within the confines of the DCU (mainstream or Vertigo), I'd say noone but Michael/Lucifer could pull it off.
If this unkillableness carries over into an neutral setting, then I'd say only Michael, Lucifer and The Tribunal (all vassals for the power of truly omnipotent beings) could kill him. If it doesn't, then really all you'd have to do is be more powerful than The Stranger, but that in itself is incredibly difficult, as although he has few feats, it's made very clear The Stranger is incredibly powerful, but he uses this to help heroes claim their own victories, rather than just turning up and taking out the bad guy.
Either way, I'd guess the unkillableness would stay on, so yeah, Michael/Lucifer/LT.