It's made clear in the film He Never Died that most people can't see the Goatee man, although our Hero seems him at various 'significant' points. When the Hero rants at him, he includes the statement that 'There is no God' so we can assume he's not meant to represent God. At the very end, he speaks (for the first time) with a rather demonic sound.
But I still am not sure who or what he's meant to represent -- the Devil? (he's at some of the nastier scenes, but ALSO at a few harmless ones.) Death? (He there for a few killings, but not all of them, and a few of his appearances are not accompanied by a death.) One of the named angels, perhaps?
I've seen a few interviews talking about the main character, but haven't seen any clear explanations as to what he is.
[Since the main character is a figure from the Christian bible, biblical info is within the scope of logical answers.]