What would inflict a beating on the Cree'Ar fleet are aforementioned battlestations, starships, and starfighters launching missile and torpedo volleys against the Cree'Ar ships.
What would inflict massive and dreadful losses to the Cree'Ar fleet would be the Hypervelocity cannons on Coruscant. A single shell might be enough to disable or destroy a single Parrow-Lin class battleship, and a rate of fire of about one shell per ten seconds, it's probably mostly these weapons that have carved down the parity between the Cree'Ar and Imperial forces.