You will not see Luffy consciously use Conqueror's Haki again until much later (the Post-War Arc/Return to Sabaody), but this Marineford moment is his first major, visible display of it.
Luffy uses Conqueror's Haki in Episode 473 ("The Warlord's Seal Broken!") during the Marineford Arc.
With Whitebeard momentarily incapacitated by a heart attack and Marco pinned down, there was no one left to stop the execution. In a final, desperate roar to save his brother, Luffy screams, which episode does luffy use conqueror's haki in marineford
While this is the defining Haki moment of Marineford, Luffy had previously used it subconsciously: Against Duval's bull, Motobaro.
This moment is crucial because it draws the attention of the heavy hitters. Ivankov, surprised by the display, realizes Luffy is not just acting on impulse anymore. It is the first confirmation for the audience—and the world—that Luffy possesses the "qualification of a king." You will not see Luffy consciously use Conqueror's
To summarize, Luffy uses Conqueror’s Haki twice during the Marineford arc:
He knocked out trained soldiers on a global stage, not just local thugs or wild animals. In a final, desperate roar to save his
While Luffy had used Conqueror’s Haki before (specifically against Motobaro the bull and at Amazon Lily), the Marineford outburst was different for three reasons: