Sakazuki is the Fleet-Admiral of the Marines, formerly known as Admiral Akainu; and has an extreme view of what he sees as "Justice". He ate the Devil Fruit that gave him the power of magma. He is one of the main antagonists of One Piece.
Admiral Akainu (赤犬) is an admiral of the Marine Forces of the World Government in the series One Piece, by Eiichiro Oda. His original name was Sakazuki, but it was changed upon his promotion to admiral. He ate a, as of yet, unnamed Devil Fruit that gave him the body of magma. Since it is a Logia type Devil Fruit, he is immune to most physical damage.
Akainu was first seen in the One Piece series during the flashback of the Buster Call attack on the island of Ohara. He was not seen again until the Marineford Arc and the war with the Whitebeard Pirates.
He is a ruthless commander that seeks to kill as many pirates as possible. Going so far as to attack his own side for not following his orders. As with all the other Marine Admirals. They are believers in "Absolute Justice".
Sakazuki "Akainu" is an antagonist in the One Piece series that was created by Eiichiro Oda. The series first began serialization in Shueisha's Weekly Shōnen Jump on August 4, 1997. He first appeared during the Enies Lobby Arc that began in Volume 38.
His first appearance was in One Piece Volume 41 CH. 397 "In Order to Reach the Future", and his first anime appearance was in One Piece - Episode 278 "Say You Want to Live! We are Comrades!!". His character in the Japanese series is mainly voiced by Fumihiko Tachiki, and the younger Sakazuki in his first appearance was voiced by Michio Nakao. The U.S. dub produced by FUNimation has not been announced.
The first real time in the One Piece series that the audience got to really see Akainu was during the war with the Whitebeard Pirates at Marineford. The intent was to execute the pirate Portgas D. Ace. Not only was he the second division commander of the Whitebeard Pirates. He was the biological son of the former Pirates King, Gold Roger.
Akainu was the last of the Admirals to make a move to attack Whitebeard's pirate crew directly. In this action he finally exposed the nature of his Devil Fruit power. He launched an attack called "Great Eruption" and melted a giant block of ice that had been cast to the Marineford plaza. His arm became magma melted the glacier into vapor with the intense heat. He seemed greatly irritated that his fellow admirals Aokiji and Kizaru had left their post.
He they rained down enormous lava rocks onto the pirates below. One was aimed for Whitebeard, but it was blocked easily and blew out as if it was a candle. Whitebeard even made such a comment, but Akainu replied that he would make him a funeral pyre.
Akainu was the man who gave the death blow to Ace. He had been disrespecting Whitebeard and Luffy didn't like the things he was saying. This had distracted Luffy enough to allow Akainu to try and attack, but Ace dove to save his little brother and took the brunt of the attack. Though they both had Devil Fruits of fire elements. Akainu's won out due to sheer level of power and heat. Ace died with a smile as he thanked Luffy and his fellow pirates to make him happy to be alive. This sent Luffy into a comatose shock of witnessing this murder, and he was easy prey for Akainu.
Akainu was ready to kill the vulnerable Luffy as well when he was rescued by former Shichibukai, Jimbei; Buggy; and other Whitebeard Pirates who were intent on saving Luffy.
Whitebeard, himself, even stepped in and struck Akainu so hard that he was cast into the structures of Marineford.
Though Luffy managed to escape, he was severely injured. Akainu was intent on killing as many pirates as possible, then a voice called for the fighting to all stop. It was a young Marine named Coby. He could hear all the voices dying around him. Whitebeard and Ace were now dead and that had been the goal. This young man didn't see the point in more bloodshed. Angered by Coby's actions for not following orders, Akainu turned on him and intended to kill. He was only saved due to the intervention of the captain of the Red-Haired Pirates, Shanks. It was Shanks that would negotiate an end to the war with Fleet-Admiral Sengoku by threatening his crew would also join the fight.
Akainu would appear again after the end of the war on an island in the New World, the second half of the Grand Line. The betrayer of the World Government, Blackbeard, had taken Jewelry Bonney captive and was attempting to barter with the World Government for a particular ship he desired. This deal was rejected when they sent Akainu. Blackbeard and his entire crew fled, leaving Bonney.
He arrived on the island and had words with Bonney. Akainu said how surprised he had been when he discovered that she had turned against the World Government. Her only reply was that she couldn't ever forgive them.
He has not been seen since.
Most of Akainu's incredible power comes from the Magu Magu no mi(Magma-Magma fruit) Devil Fruit he consumed. It is a Logia type. These are some of the most powerful, since they change the body of the user into elements. This grants them a certain level of immunity to most physical attacks. Akainu now has a body of magma and can generate intense heat.
As with all admirals, he has a special ability called Haki. It's a dormant power in all creatures, but few can ever tap.
Ryusei Kazan (流星火山 Ryūsei Kazan, literally meaning "Meteor Volcano") -Akainu creates a great number of magma fists that he fires into the air in order to let them rain down upon the battlefield, causing enormous amounts of area damage
Inugami Guren (犬噛紅蓮 Inugami Guren, literally meaning "Dog-Bite Blaze"): Arguably the source of Sakazuki's nickname, Akainu creates a wave of magma, shaped like a dog's head, and launches it against his opponent. It was first used against Whitebeard.
Dai Funka (大噴火 Dai Funka, literally meaning "Great Eruption"): Akainu's signature technique, he transforms his fist into one made out of pure lava before throwing it forward, like an over-sized rocket.