Darker Hero for the main continuity (similar to huntress was for example often handled).
Potentially Anti-hero in Elseworld's (if he can actually permanently kill of some some bigger villains).
Villain doesn't make much sense and wouldn't really work on the long run. He knows the secret identities and weaknesses of a lot of DC heros, you would have to massively dumb him down if he should be around as a villain on the long run. (Of course he gets often dumbed down in Batfamily comics as well...)