Sakazuki formerly known as Akainu is one of the two main antagonists of One Piece (alongside Blackbeard also known as Marshall D. Teach). He is notable for murdering Monkey D. Luffy's adoptive brother Portgas D. Ace, making him Luffy's marine arch-nemesis. He is the main antagonist of Marineford Arc and the remainder of the series.
Why He Sucks
First of all, he lacks empathy. The time when he was a vice admiral, he destroyed a ship leaving the island carrying civilians.
To make matters worse, he literally KILLED HIS OWN SOLDIERS! One example includes almost killing Koby just because he was distraught over his fellow soldiers and wanted the war to end. And he would be died if it wasn't for Shanks saving his life.
When Blackbeard and his pirates arrived and destroyed Marineford, he did not help Sengoku battle them.
He claims that he is a hero, when he is a big villain since he bullies pirates a lot.
He is notable for killing Ace and shows no remorse for that. Thus caused Luffy to have a mental breakdown, even after the Marineford War.
Speaking of Luffy, he is responsible for his chest scar as well.
He ordered the Marine bases to turn Fujitora away just because he did not kill Luffy and Law.
He mocks Whitebeard in front of his son, Ace.
He made Squard, a fellow pirate of Whitebeard stab his own captain.
Instead of fighting Whitebeard, he hid under the ground to avoid a taste of his own medicine for killing Ace.
His appearance is based on the Japanese actor, Bunta Sugawara.
His favorite foods are rice and red pepper.
According to the creator of One Piece, he was so powerful that he could end One Piece in a year.