A O

A.O is an infamous New World pirate who allied himself with Whitebeard.

Appearance
A.O is a very tall man with a long square shaped face, hollow eyes under prominent eyebrows, dark sideburns that go all the way down to his chin, and greenish long wavy hair. On his head he wears a striped bandanna with a standard tricone captain's hat with what appears to be his Jolly Roger on it, a skull wearing an animal-like hood. He also wears a dark blue, open shirt with the sleeves rolled up and a ruffled collar, and elaborate earrings made up by three little jewels each on both ears.

Abilities and Powers
A.O is a fearsome pirate who has managed to make himself an infamous reputation in the New World, and to ally himself with Whitebeard. He was seen charging forward with his fellow allies wielding an unseen weapon above his head with both hands.

Marineford Arc
In the past, he allied himself with Whitebeard. A.O and his crew are first seen, along with a fleet of 42 other infamous pirate crews, allied with the Whitebeard Pirates, attacking Marineford to save Portgas D. Ace from his execution. Later, he and the other New World pirates allied with Whitebeard Pirates were attacked by the Pacifista army. After Squardo stabbed Whitebeard and claimed that Whitebeard sold out his allies to save Ace, A.O began to doubt Whitebeard. After Whitebeard proved his loyalty by giving the pirates an escape route, A.O was happy to know the truth and continued fighting the marines. After the siege wall was raised and Akainu melts the ice with his magma powers, A.O boarded Whitebeard hidden ship and entered the plaza with the help of Oars Jr. Later he followed Whitebeard's order in supporting Luffy and was rejoiced when Luffy managed to free Ace. However, their excitement was short-lived when Admiral Akainu provoked Ace and took his life. When the Admiral aims for Luffy's life, A.O and the other pirates made protecting Luffy their top priority. After Shanks arrived and called for a ceasefire, A.O and the other pirates left the battlefield.

Post War Arc
On an island somewhere in the New World, A.O and the other pirates attends Ace's and Whitebeard's funeral.

Trivia

 * His name is given in the anime's credits, not in the manga, and therefore cannot be considered be canon.