Sakazuki

Admiral Akainu (赤犬大将, Akainu Taishō), formerly known as Vice Admiral Sakazuki (サカズキ中将, Sakazuki Chūjō), is an Admiral of the Marines, one of only three to hold such a position and subordinate only to Fleet Admiral Sengoku. He was first mentioned by Robin during the initial encounter with Aokiji.

Appearance
Twenty years ago at the Ohara incident, he wore a simple white marine cap and he also wore a dark gray hood that seemed to be a part of a cloak he wore beneath his suit, or marine coat. Like any other high ranking marine, he was dressed in a simple white/gray suit with a white marine coat draped over his shoulders. His entire face was not seen during his appearance, as it was hidden by his cap.

At the execution of Portgas D. Ace; Akainu is seen wearing a dark-colored suit, with a flower greatly resembling a rose on the left side of his jacket; underneath this he wears a shirt with floral print. He is also wearing black gloves and boots and the same Marine cap covering the top half of his face.

Akainu has a square-shaped face with hollowed out cheeks. There also appears to be a tattoo on the left side of his chest, but it is largely obscured from view by his shirt. However, from what is seen, it appears to contain numerous images of flowers integrated into the design. He appears to be just as tall as his fellow Admirals, Aokiji and Kizaru.

Personality
We have to be thorough! If even one of those scholars made it onto that ship, all of the sacrifices we've made would be for nothing! We must eliminate the very possibility of this "evil" existing!!

— Akainu's view on destroying the ship.

Akainu is a firm believer in "Absolute Justice", ruthless to the edge in maintaining justice. Of the three Admirals, he is the only one who has maintained a dead-serious disposition in all of his appearances.

Akainu's beliefs led him to go as far as destroying the refugee ship simply due to the possibility of even one scholar sneaking on board. His logic is that if even one of the scholars of Ohara had escaped with it, the mission would've been a failure, much to the dismay of Aokiji, who called him a fool for overdoing things. Akainu is also willing to lie to his enemies, and pretend to be sympathetic with them, in order to achieve results, as he managed to deceive Squad through Sengoku's master plan.

Additionally, he seems to have no tolerance for Marines who desert their post, even though that soldier did so for the sake of his beloved family, to the point of killing them using his lava-based unnamed Devil Fruit powers.

Prior to Sengoku making it public, Akainu is one of the few who knows that Luffy is Dragon's son. Whether he has some relationship with Dragon or if some of the Marines know that Dragon is Garp's son is unknown. As a believer of Absolute Justice, Akainu deems that Luffy's mere existence due to being Dragon's son is enough to be a threat to the world, and must be eliminated.

Abilities and Powers
As an Admiral, Akainu is able to command vast number of Marine troops that are under his rank. Most of all, he has the ability to order a Buster Call attack on any island. It appears that Akainu and his fellow Admirals have very acute hearing; they were able to hear activity underwater before anyone else.

Devil Fruit
Akainu possesses a yet-unnamed Devil Fruit which gives him control over molten rock that can be fired at long range in the form of meteor-like fists.
 * Dai Funka (大噴火, Great Eruption): Akainu transforms his right fist into one made out of pure molten rock before throwing it forward, like some oversized rocket. The explosion causes volcanic rock to hit the ground, in a method similar to meteors. This was first seen when he used it to evaporate an iceberg hurled at his fellow Marines by Jozu. According to spectators, the battlefield resembled an apocalypse after this one attack.
 * Ryūsei Kazan (流星火山, Meteor Volcano): Akainu creates a great number of molten rock fists that he fires into the air in order to let them rain down upon the battlefield, causing enormous amounts of damage. This looks like a cross between a meteor shower and a volcano eruption. This was first used to destroy the ice floor Aokiji created along with the pirates who were standing on it. He managed to take out Whitebeard's flagship, the Moby Dick, with this technique.

Ohara Incident
He was known as Vice Admiral Sakazuki before his promotion. He was present at the Ohara incident, being one of the five vice-admirals, leading the Buster Call offensive. He ordered the destruction of an evacuation ship of civilians and soldiers, claiming it needed to be destroyed in case a single scholar managed to sneak on board (an action that horrified even Spandine).

Current Events
Vice Admiral Momonga mentioned to Boa Hancock that the three Marine Admirals, including Akainu, will lead the Marines against the Whitebeard Pirates following the announcement of Portgas D. Ace's execution. Akainu was seen sitting beneath the execution platform of Portgas D. Ace with his fellow Marine Admirals.

Akainu stepped into the battle when Jozu hurled a massive iceberg, displaying abilities to control volcanic rock by launching a fist made of lava to destroy the iceberg and sending small burning rocks flying all over the place, destroying one of Whitebeard's ships.

He is later seen confronting a Marine officer who is fleeing from the battle not wanting to die out of concern for his family. Akainu attacks, and brutally kills, the Marine officer for this "cowardice", much to the horror of Coby and Helmeppo who were watching (having nearly ran into the Admiral themselves doing the same action). Akainu then receives a report on the Den Den Mushi that the preparations for Sengoku plan are set.

Luffy's arrival at Marineford has Admiral Akainu commenting that, as the son of Dragon, Luffy is the one pirate who must be eliminated at all costs.

During the battle, following Sengoku's orders, Akainu talks to Captain Squad, making him believe that Whitebeard has betrayed his allies, trading their lives with Ace's one. He demonstrates his words making Squad notice that the Pacifistas has attacked everyone in the bay but Whitebeard's pirates, this being also part of Sengoku's plan. He tells Squad he doesn't agree with the plan of sparing Ace's and Whitebeard's life, and offers him the chance to save himself and his own crew if he kills Whitebeard. Because of his deep hatred for Gol D. Roger, who killed his first crew, Squad believes him and attacks Whitebeard, stabbing him in the chest.

Whitebeard survives Squad's attack, forgives his ally and starts a massive attack against the Marines, using his Devil Fruit's powers. Akainu, along with Aokiji and Kizaru, manages to stop Whitebeard's seismic waves directed to the platform on which Ace is chained. When the steel wall is finally risen around the pirates, Akainu starts to attack the pirates with his Ryūsei Kazan.

Much later, when Luffy is hurled over the siege wall and lands before the execution platform, Akainu sneers before commenting on how bold the son of Dragon was.

Translation and Dub Issues
Sakazuki's alias, "Akainu", means "Red Dog" in Japanese.

Trivia

 * The way Akainu's character design is drawn resembles the famous Japanese actor, Bunta Sugawara. Akainu's real name, Sakazuki is apparently based on the three movies of Bunta Sugawara with "Sakazuki" in the title.
 * His name and other Admiral names (Aokiji, Akainu, and Kizaru), are taken from Momotaro legends (Momotaro met Pheasant, Dog, and Monkey as friends to accompany him in his journey)
 * Before being revealed in chapter 554, Akainu's abilities were the center of many myths among fans.