I used to think it was advanced conquerors, but the long black lightning streaks weren't shown, so it's deff not conquerors for sure. On top of this, his fist didn't seem to make contact with Pizarro's fist, so I'm sure he used advanced armament. Now some of y'all might not believe it since the layer, coating, whatever you wanna call it when using advanced armament wasn't shown, but Oda has drawn Luffy using Red Roc (an advanced armament technique) without actually drawing it.