Thor versus Mephisto? This should be a good, extended arc with all kinds of implications!
Or not.
It’s a done-in-one about Mephisto literally serving as the devil on New Yorkers’ shoulders, telling them to steal stuff and commit other types of crimes. Thor keeps stopping the crimes, so M brings Thor down to Hell, where Thor hits him in the face with Mjolnir.
(Great idea+middling execution) x Jim Shooter’s edict that stories should be done in one issue=Lost Opportunity.