Law had already used Gama Knife on Kaido and it didn't do much damage, Gama Knife does internal damage and as we saw Law performed a much larger and stronger version of Gama Knife on BigMom 2 chapters ago which broke BigMom's ribs, last chapter he did an even larger and strongest version of Gama Knife, the puncture wille
(Gama
Kinfe (on Kaido and Flamingo) << Gama
Sword (on BigMom 2 chapters ago) <<< Gama
Sword Island Size (on BigMom last chapter))