I think it’s safe to say that everyone knows who Batman is. He’s a legendary Superhero who’s had more power ups than some characters have had appearances. HIM is a strong demon, but he can’t hope to match up to Batman’s Yellow Power Ring. Its solid constructs will keep HIM on the defensive throughout and Batman’s sharp wit will allow this advantage to be enough for victory. You can’t stop the Dark Knight so easily. Batman wins.
Suggested by iKnowledge John Constantine is a skilled magic user, but one who isn’t quite as powerful as the heavy weights like Dr. Fate or Strange. He’s given a lot of cred since the guy knows the rules and can adapt to magic really quickly, but I wouldn’t want to have him around in a fight. HIM is a demon so John is in his area of expertise, but he’ll be too busy dodging lasers and trying not to get squashed to really do anything about the situation. He’s just outmatched in this fight and I don’t think he’ll be able to get on the offensive. HIM wins.