Kingdom Come gog was given power from all the quintessance and thus could defeat any of them in one on one combat but not combined.
Beings that gave him power are as follows, shazam the wizard, phantom stranger, DC zues, and ganthet.
He bested the following with relative ease
Mr M i believe he killed Mr M
Flash who was so fast he could be everyone at once in his city maybe even beyond i heard he was fast enough to traverse dimensions
He killed the strongest GL who was i believe allen and he had armer made out of the starheart of from it he also created a city or something named Oa near the planet earth i believe
Superman- he is stronger then normal supes i believe.
Wonder women i dont have to much info on her in this saga
also he defeated a berage of other characters. in the end he was stoped by a being who had controll over hyper time they say superman prime is stronger but does prime have controll over hyper time.
Gog can time travel too
Gog also sated he allowed himself to be defeated cause his mission of killing superman had become boring or whatever.