I would Mazahs was more powerful by the end of the forever evil run.
What I am wondering is if the Alexander Luthor of that Earth was born with the power to steal other super powers, or he developed a technology that allowed him to do so.
Or was Alexander Luthor that earth's Shazam (Mazahs), which wouldn't make much sense since he stated that he stole the powers of shazam.
Well we know from the earlier issues of Forever Evil that batman said "Why should we keep him alive, after he tore us apart, turned us against one another". Maybe Alexander Luthor was a part of their League of villains, which begs the question what power did he have? He must have had some sort of power because Superman respected power, and hated weakness.
Was Alexander Luthor a powerless human in earth 3? I thought in the old comics Lex Luthor of Earth 3 was the only good guy, and everyone else was a bad guy? Maybe he developed a technology that let him kill, and absorb the powers of the villains. Maybe he went too far in his crusade as the only hero against a world of villains?