I expected better tbh. Big Mom was seen as this person who cannot be damaged in WCI. "Iron Balloon" remember that? They made a whole big thing about cracking a picture frame just to hurt her. Now shes taking brunt force attacks by Kidd and somehow its working all of the sudden. Law I can understand cause he's damaging from within. His DF has always been beyond op. Kind of wanted Oda to give Kidd more here instead of giant mechs and now some type of cannon. Ah well...
do the math and you will see that they are not simple metal constructs.