GalacticStorm
Smart Alec Know-It-All
Prime says "Can i change all of them if i kill this monster?"
Prime doesnt claim any ability to change reality directly. He reasons after what happened with the evil superman that taking out the source of the nightmare worlds, would have the same effect i.e causing good to become dominant over the 52 worlds.
He explicitly highlights it as a possible side effect from taking out DK who we know is maintaining said worlds.
SBP attacks DK and Good starts to take hold and SBP sees glimpses of whats possible if good triumphs.
DK gets his bearings meaning evil takes hold hence Prime seeing a return to the evil/nightmare versions of said worlds.
After attacking DK again and finally defeating him, good/anti-crisis prevails and the worlds are changed.
Its presented as a side effect of taking out DK. Not an outcome SBP possesses an ability to directly bring about.
He states: "Can i change all of them if i kill this monster?"
SBP attacked DK thereby disrupting his hold over reality resulting in good prevailing as a side effect. That is all.