Mephisto Vs Shazam

They're realms are...mixed (I don't know anything about Shazam so sue me) somehow so they're both at full power.

Old man Shaz.

Who wins?

Mmmmh... Hard one. I have to say Shazam since he has better feats, however nobody outside Galactus has beaten Mephisto on his realm.

Depends on who has better resistance to the other's power...I say based on the fact that mephisto is physically much harder to destroy if not impossable, he wins.