"Peak" technically means Volthoom is utilizing *the* willpower nexus(ie. Hal) to tap-into the entire timeline... Which, as I explained in another thread, allowed him to literally become DC's proverbial "Hand of Creation" -- the mysterious Hand that originally birthed the whole of DC. So in that case, he wins.
Without that focal point to directly tap, however, I don't see Volthoom beating this iteration of Krona. He literally IS a universe. /shrug