User blog comment:Sysage/Blackheart vrs Thor/@comment-4537153-20120529061336

Thor has held his own against Mephisto in his own realm and Blackheart has the same power levels on Earth as he does in his own version of hell so this would be very close cosidering the different amount of abilities and high power levels both possess. The difference maker is that Blackheart would not care about anyone or anything during the fight, which Thor would. Too close to tell but since Thor has a winning track record against high powered demons and cosmic entites, I'd go with him by a small margin.