Hades should win mid-high diff, mostly because of his overwhelming offense. Sure, Mard may have dodged attacks from 2-3 enemies at the time and blocked an attack from CSK, but I doubt he could do it forever with a DOZEN of Nemesis demons + Hades' arsenal of devastating spells boosted by his Devil's Eye (even without this boost, he could blow up 1/5 of Tenrou Island with an Amaterasu 100). And Mard's Thorns may be enough to pierce Hades since they could hurt CSK, but seeing how Natsu and Gray easily dodged them, they're probably not very accurate against smaller targets, and Hades' spells and Nemesis demons should be more than enough to protect him from the thorns he can't dodge. Mard's only chance of winning is with Memento Mori, but if I include it, I'll have to include Grimoire Law as well to remain fair. They both seem to have the same casting time and could both 1-shot the other, but seeing Fairy Law's feats (Makarov almost wiped out a whole ARMY with it, and Grimoire Law is basically a dark version of it), Grimoire Law must have at least 100 TIMES more range and zone-effect, so much it could make Hades win while Mard Geer is still flying to reach him.
