Can't see that happening, Mephisto aint that good, he's been punked to many times by people lesser! PC Darkseid on his own could handle Mephisto, the guy took out Time Trapper and Mordru, for crying out loud, and added their powers to his own, and enslaved a full planet of Daximites under his will! That show's you what time of power he wields, adding Dark Phoenix is overkill!
Darkseid, as current Darkseid (to which this is the cover to Final Crisis #4, which Darkseid has let loose the ALE and enslaved the earth and all it's population, hero and villain alike! Then yeah, I believe he'd give Mephisto a good stomping himself!