Stranded on the island of the Kuja Pirates, Luffy displays his rare trait to a shocked audience of Haki users.
During the raid on Onigashima, Luffy is knocked off the rooftop by Kaido. He remembers Hyogoro's lessons and has a crucial realization: to truly damage Kaido, he needs to coat his attacks with Advanced Conqueror's Haki. After his epiphany, Luffy ascends back to the rooftop and unleashes a gushing wave of Supreme King Haki, now understanding how to use this advanced technique for offense. which episode luffy use supreme haki
— Upon returning to Sabaody, Luffy casually uses Haki to knock out the "Fake Straw Hats" and their recruits without lifting a finger. Showdown at Fish-Man Island: Episode 554 Stranded on the island of the Kuja Pirates,
Confronted by Hody Jones and an army of 100,000 New Fish-Man Pirates, Luffy walks past a worried Jinbe and Sanji. He releases a massive, sweeping wave of Supreme King Haki. Instantly, 50,000 enemy soldiers faint, cutting the opposing army exactly in half in seconds. Episode 716: Clashing with Don Chinjao After his epiphany, Luffy ascends back to the
When asking "which episode does Luffy use supreme haki," fans are really asking, "When does Luffy become a top-tier fighter?"