Bat-Mite could have potentially been the most powerful individual in Earth-One's universe... well until the point when he left it to journey to Earth-Prime, never to return.
Gifted with reality-altering abilities from some undefined dimension where he came from, this irritating imp became fixated on his idol, Batman, seeking to "improve" his hero's stature and capabilities by manipulating criminal around him into being bigger and better threats which the Caped Crusader would need to work harder to defeat. After a dozen such misadventures, including a few where he teamed up with Mr. Mxyzptlk when the pair faced Batman and his pal Superman, Bat-Mite took his cue and left for other universes.
In Earth-Two's reality, there was the Thunderbolt who was a member of the Justice Society of America. The Thunderbolt was known as Oswald in his native dimension. Like that diminutive Mite, T-Bolt had an impressive array of abilities which aid that world's Batman and the Justice Society. Meanwhile, Thunderbolt's son Shocko was to his world what Earth-One's Quisp was to his, although aiding a different blonde instead of Johnny Thunder in the form of Aquaman.
Thunderbolt no doubt came to the notice of Earth-Two's Mister Mxyzpltk, who like his own counterpart was drawn towards trouble when Mxyzptlk and Bat-Mite commenced their rivalry. The possibilities of all four of these beings meeting is simply to mind-blowing to ponder, given there dubious nature towards humanity from time-to-time.