Busoshoku (武装色) is Haki that strengthens one's offense and defense like armor.
With it, it can defend them against a Devil Fruit users (悪魔の実) abilities while also allowing them to potentially strike back! (This is Armament haki... It has nothing to do with Conqueror's haki)
Law was unable to cut through
Doflamingo's usage of Busoshoku Haki, with the latter catching the former's sword and stopping Law's attack despite being inside of Law's ROOM.
[20] Haki being used as a deterrent to this fruit's effects was further proven in the
Wano Country Arc, where Law confirmed he was unable to displace either Big Mom or Kaido around due to their far superior Haki.
[21] (
Not trying to spoil myself)
It's lol he has stronger haki it gets resisted...