Haoshoku Haki (Conqueror's Haki). This is a major milestone. Unlike the first time, Luffy uses this consciously and with intent to protect his friends. It shocks everyone on the battlefield, as using Conqueror's Haki consciously is a sign of a true threat.
"W-What is this pressure?!" a Marine screams. luffy using haki in marineford episode
Luffy’s display of Haki shocked everyone, from the Admirals to the legendary Whitebeard himself. Haoshoku Haki (Conqueror's Haki)
Admiral Akainu noted that Luffy used the power unconsciously, while Sengoku and Aokiji were visibly shaken by the rookie's hidden potential. luffy using haki in marineford episode