While its moot, actually, no, I don't think Mephisto would actually be able to create Kurse. While the exact power tiers are different in the movies than in the comics, they are still largely proportional. And in the comics? Mephisto is not powerful enough to create someone who can kick Thor's ass. Mephisto *himself* is only powerful enough to usually stalemate; if Kurse were loosed in Mephisto's realm, he'd rampage and likely be unstoppable until Mephisto wised up and dimension dumped him somewhere else.