[quote=@ZAVAZggg]
[@Dynamics]
Maybe I could make him immune to just Annihilation, seeing as how God has the final say over the existence of a being He created, but allow him to be killed. 
[/quote]

Sorry, let me clarify that; I think I worded it strangely. When I say "annihilation," I mean more in the sense of being hit with so much sheer force that there's no material left that can recover; I didn't mean to imply that someone is just going to erase them.

There's a system for intangible beings that we could apply if you want to go that route. For example, if the physical aspect of him is destroyed, he could go into an intangible ghostlike form until he can get enough energy to restore the physical aspect. So that way, it's not technically "100% unkillable," but it's a lot harder. Of course, you don't have to do that if you don't want to—there's a lot of room to maneuver.