Sakazuki

Admiral Akainu (赤犬大将, Akainu Taishō), formerly known as Vice Admiral Sakazuki is an Admiral in the world of One Piece, one of only three to hold such a position and subordinate only to Fleet Admiral Sengoku. In English, his name means "Red Dog."

Appearance
Like any other high ranking marine he is dressed in a simple white/gray suit with a white marine coat draped over his shoulders.

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.

His entire face was not seen during his appearance, as it was hidden by his cap.

At the execution of Portgas D. Ace, we see Akainu wearing a black suit with a flower greatly resembling a rose on the left side of his shirt. He is also wearing black gloves and boots and the same Marine cap covering the top half of his face. There also appears to be a tattoo on the left side of his chest, but it is obscured from view by his shirt.

Personality
Akainu is a firm believer in "Absolute Justice", going 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.

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.

Powers and abilities
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. In addition to this, given that he holds the same rank as Kizaru and Aokiji, it can be assumed that he commands comparable fighting abilities to those two.

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 3 Marine Admirals, including Akainu will lead the Marines against the Whitebeard Pirates following the announcement of Portgas D. Ace's execution. Akainu was recently seen watching over the execution platform of Portgas D. Ace with his fellow Marine Admirals.

Trivia

 * 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)