As the Straw Hat captain, he’s had to level up his skills to take on tougher foes, and learning Observation Haki, Armament Haki ... making him a real threat to the Yonko. Conqueror’s Haki ...

He is the 33rd son of Big Mom and a user of Armament Haki ... and that is Observation Haki. He utilized this skill actively in the Wano Country arc, although he had no real control over it.