If Kal-EL did turn out like that then he would indeed be unstoppable by the heroes in Marvel (except maybe somebody like Professor X, but even that is doubtful since Doom seems to be able to resist telepathic control) .
However, it is in no way given that Kal-El would turn out like that. It is also possible that he would turn against his 'father'.
Are character traits innate or educated? Big question...
THAT would be a scary Superman, one whose weakness to magic eliminated!
Greek K not an option, as none would even know about it, maybe red Sun still>