Warning: Contains spoilers for One Piece #1037
The battle for Onigashima has finally reached its climax in One Piece. With the top executives of the Beasts Pirates defeated the only fight left to settle is the one between "the world's strongest creature", Kaido, and Luffy. In order to defeat the most powerful foe he has ever faced, the captain of the Straw Hat Pirates is finally unleashing his true potential on the battlefield.
The world of One Piece is full of mighty fighters, from fearsome pirates to stalwart Marine officers, and, in true shonen manga fashion, Luffy and his crew had to constantly overcome their limits. They faced their biggest challenge in the New World, the second half of the Grand Line, dominated by the strongest individuals in the world, including the Yonkou, the Four Emperors who stand on top of all the pirates. All the crew went through hellish training to compete with these monsters, but perhaps none has grown more than Luffy, who mastered the abilities of his Gomu Gomu no Mi Devil Fruit, and the mysterious power known as Haki. During his fight with Donquixote Doflamingo, Luffy debuted his Gear Fourth form, which let him overcome the powerful Shichibukai, but even that was useless against Kaidou. However, after further training that lets him master Haoshoku (Conqueror's) Haki, Luffy is finally able to stand toe to toe with the Emperor.
Chapter #1037 of One Piece focuses mostly on the third (and supposedly final) clash between Luffy and Kaido. The two are exchanging blows and seem evenly matched: after training in the Udon prison, Luffy is able to "infuse" Haoshoku Haki in his attacks, a quality displayed until now only by a handful of top fighters in One Piece, including Kaido and legends from the past such as the Pirate King, Gol D. Roger, and Edward Newgate, Whitebeard. Haoshoku is the rarest form of Haki, possessed by only one in several million people, and it cannot be attained through training. It is said that whoever is gifted with it has the qualities of a king, but only recently the manga has shown its application in combat. "Infused" Haoshoku attacks can harm even extremely resilient individuals such as Kaidou and his officer King, and Luffy is putting the technique to good use. However, the aspiring Pirate King seems to still be in the process of unlocking his true power.
In his current fight with Kaido, Luffy hasn't used what was until now his most powerful technique, Gear Fourth, nor the "Snakeman" attack that allowed him to defeat Charlotte Katakuri, his strongest opponent until now. In fact, Luffy's attacks fuse his Gear Second and Third forms. His arms and feet are giantly inflated, like in Gear Third, but he retains the speed of the Gear Second, with the trademark steam of this form coming out of his body. The advantage of having "upgraded" his previous techniques is that they don't consume the same stamina that Gear Fourth did, which gives it a drawback in the form of a short time limit. The reason behind Luffy's further power-up could be that his mastery of Haki has increased his overall strength, making him less reliant on flashy techniques, or that he is close to "awakening" his Devil Fruit, a rare process that drastically increases the fruit's user abilities.
After seeing both Sanji and Zoro unlocking a new level of strength in their fights against Queen and King, it is only natural that Luffy proves why he deserves to be the captain of the Straw Hat Pirates. Fans will have to wait for the next chapter of One Piece to see if Luffy's new powers are enough to defeat Kaido, who has beaten him twice already and is known as the strongest creature in the whole world.