As far as character statements are concerned, it was certainly implied that Superman Prime possessed omnipotent-esque power. For instance, when he finally returned back to earth after his initial self-exile, he'd already obtained powers from the Source. Then he sun-dipped from the 700th century all the way to the 867th century(and we know how powerful he becomes after just a few seconds of sun-exposure. Now imagine a year... a decade... a century of sun-dipping
!) On top of all that, he was also gifted with the last GL ring. So yeah, when you consider all of the aforementioned, the uber comments made about him start making sense, imo.
However, despite having such a high level of implied power, his only real feats were destroying Solaris(who had already been extensively injured/weakened by S1M), and resurrecting Lois with the help of a 5-d Imp... But I'd say his best 'feat' is that he acts as the power battery for every single member of the Superman Dynasty, after the 700th century--- ie. Superman Prime is to S1M and the Superman Dynasty, what Galactus is to Surfer and the rest of his Heralds.
