In the One Piece series, Luffy's use of Conqueror's Haki, also known as Haoshoku Haki or "Supreme Haki," is a significant and interesting feature of his character. This powerful form of Haki allows Luffy to intimidate and knock out others who are weaker than him.
Luffy first demonstrates his Conqueror's Haki during the Marineford Arc (Episode 388 and 389, and more notably in Episode 391) when he is trying to protect his friends and particularly when he's fighting against Donquixote Doflamingo's subordinate, however the most pivotal and clear demonstration is during the Fishman Island Arc doesn't occur but rather during the Dressrosa Arc. which episode luffy use supreme haki
If you have been following the Wano Country arc of One Piece, you have likely heard a new, electrifying term floating around the fandom: Supreme Haki (officially known as Haoshoku Haki or the Color of the Supreme King). Fans are constantly searching: "Which episode does Luffy use Supreme Haki?" In the One Piece series, Luffy's use of
Wano Country — advanced, sustained and combined uses Which Episode Does Luffy Use Supreme Haki
This is likely what you mean by “using Supreme Haki” as a fighting style.
It started as a low hum, vibrating through the soles of his sandals. Then, it erupted.