According to an interview with Eiichiro Oda, he stated that if Akainu were to become the protagonist, he is so strong that he could end the One Piece series within a year.
Akainu ate the Magu Magu no Mi, a Logia-class Devil Fruit which grants him the ability to transform his body into magma and manipulate it at will. The main strength of this Devil Fruit is that it allows the user to produce magma to attack their opponents with. The intense heat can vaporize an iceberg instantly and boil the seawater that the magma lands in.
Akainu’s ability is naturally of a higher order than Ace’s pyrokinetic abilities, as the higher heat and smothering abilities of his magma allowed him to successfully harm Ace despite Ace’s Logia-defense, and ultimately kill Ace due to this superiority.
During the decisive ten day battle on Punk Hazard for the position of fleet admiral, Akainu showed the furious power of his Devil Fruit as he changed the weather of one side of Punk Hazard and left it in a blaze. Because of this, many fans speculate Akainu has awakened his Devil Fruit.
