Now another of the greatest showing of Guardians' power comes from Zero Hour. Remember at this point CPB was just a focus for Guardians' own power as shown in Secret Origins 22.
Hal had absorbed chronal energies left after COIE to destroy time stream. Here he destroys an entire universe by opening an entropy rift. Later Extant says there are other entropy rifts he was not responsible for.
Then he starts creating his own creation using the power of Guardians. You will notice the green hue in the globes of energies which were solidifying as entire galaxies.
Spectre and the heroes fought Parallax, the heroes absorbed the plasma universe. Hal defeats Spectre but the effort lefts him weakened and the heroes prevailed.
Although it was revealed later that he used only a minute part of the power of the guardians to reignite the sun and the power of guardians is infinite.
Later the power of CPB were used to give Kyle Rayner the power of Ion where he was literally omnipresent throughout time and space and able to alter reality on fundamental level. Ion later exhausted his power returning his power to CPB and resurrecting the Guardians.
Now for Geoff Johns era Guardians. First the origin of the Guardians and how they removed emotions from themselves and gave it to Volthoom turning him into the very light which created the universe.
Current Guardians are like solar system level to be honest, classic was ridiiclously powerful but modern version of them haven't shown feats on that type scale yet. basically like galaxy scale feats
A full-powered Prime's heat vision hits a Guardian, and though it wounds him, it is stopped by the Guardian's shoulder.
This is particularly notable given how powerful Prime's HV was earlier in the story in Sinestro Corps: Superboy Prime, when it shot right through Superman's chest while Prime was heavily weakened and deprived of sunlight.
Guardians battle and stalemate Nekron, stop galaxies from destruction, defeat Krona after Nekron is distracted by Hal, seal the rift between universes and return the whole universe to its original state when it was near destruction. Beastly feats.
Guardians vs Guy Gardner with Hand of Krona and later entire GLC, Larfleeze, White Lantern Kyle, Red Lantern Corps with Manhunters. All of this while controlling almost a third of the universe with their minds.
A gargantuan feat from the preview of Green Lanterns 50. A random Guardian spreads his consciousness across all that is, was and will be across the cosmos.