Katakuri's offense is roughly G4 (pre ryou) level, easily above G2/3.
-His awakened (power) mochi attacks were comfortably countering Kong Gun level attacks
-His regular (non awakened) base attacks > snakeman's regular attacks
His offense is levels above Doflamingo's. Luffy was already looking trashed before power mochi even came out, he was on some "willpower" juice.