Akainu is the current Fleet Admiral of the Marines. He came to power after defeating his fellow Admiral, Aokiji, in one of the longest battles in One Piece. Akainu's promotion affected not only the Marines but the entire One Piece world. Akainu is a follower of Absolute Justice, which means that he doesn't have any kind of sympathy toward criminals. This was perfectly demonstrated during the Marineford arc, when he continued to chase pirates even after the Marines had secured the victory.
In addition to being ruthless toward criminals, Akainu does not hesitate to kill fellow Marines or innocent civilians if they try to interfere with justice. Before he became an Admiral, Akainu destroyed the ship that was carrying the civilians of Ohara. He stated that it would be too big a risk if even one scholar managed to get on board the ship. Clearly, Akainu is one of the best villains in the series, but where does he rank in terms of strength?
The Strongest Logia Power
One thing that all Admirals and Fleet Admirals have in common is their ridiculously powerful devil fruits. From Kizaru to Sengoku, every last one of them has an extremely powerful devil fruit, and Akainu is no exception. At some point in the past, he ate the Magu Magu no Mi, which is a Logia-type devil fruit. It allows him to create and control magma at will, making it offensively the strongest Logia-type devil fruit.
It is reasonable to assume that after so long in possession of the devil fruit, Akainu has gained complete mastery over it, and has most likely awakened it. So far, he has mainly relied on his devil fruit in fights, which is a further indicator of his excellent control over the Magu Magu no Mi. Considering the fact that he has one of the strongest devil fruits in the entire series, has Akainu done justice to its power?
The Top Marine
Akainu's rise to the highest echelon among the Marines has not been a fluke. He has the feats to back up his claim of being the strongest Marine in the series. Akainu made his debut in the Marineford arc, where he carefully used his devil fruit powers to cause chaos among the pirates. When the time came for Akainu to get involved in the fighting, he didn't hesitate. Akainu went after the big-name pirates, and his biggest moment came when he finally killed Portgas D. Ace. One would think that killing Ace would have been reason enough to stop the war; however, Akainu was not satisfied. He decided to go after Luffy, who had to be saved by Jimbei and Marco.
Vista and Marco even tried to injure Akainu, but their Haki proved to be weak. Whitebeard, who had also joined the battle, quickly became enraged once he learned about the death of Ace. Whitebeard appeared behind Akainu and started pummeling the Marine without any problems. Akainu had almost no response to the Emperor's power, but he wasn't ready to back down from the fight. In an attempt to kill Whitebeard, Akainu burned off the left side of the pirate's face. However, Whitebeard was not even fazed by the attack, and he continued his assault on the Marine.
Akainu was humbled by the Emperor, yet that didn't stop him from attacking the other pirates. In fact, one of Akainu's attacks made contact with Luffy, which left the pirate in a very critical condition.
Aside from his involvement during the Marineford arc, Akainu has rarely received any screen time. His fight against Aokiji, which lasted for multiple days, was not shown. When he went to take Bonney, the Blackbeard Pirates ran away instead of confronting him, which is a huge testament to his power. After becoming the Fleet Admiral, Akainu's power increased even further. However, due to his current position, he cannot leave the headquarters and show off his strength. Needless to say, Akainu hates this restriction that came with his new position. So, will Akainu never be involved in a major battle again?
Akainu's Role In The Final Saga
As previously stated, Akainu's screen time has been minimal, and the reason is that Oda wants to save him for the very end. Akainu is definitely going to get involved in the action during the final saga of One Piece. He needs to be taken down for the world to be a truly free place. So, the question is: who will fight the magma monster?
The most prominent idea is that Akainu will be defeated by Luffy because of what the former did to Ace. While it is a fair reason, there are other characters who would be better suited for the fight. Sabo, for one, would be the perfect match for Akainu. As Luffy's elder brother and the chief of staff of the Revolutionary Army, Sabo has multiple reasons to beat Akainu. Another theory pits Monkey D. Dragon against Akainu because both of them are at the top of their organizations and want to change the world in their own ways. From his recent appearances, Akainu is clearly itching to go out and kill criminals, and judging by the current pace, it won't be long before he gets involved.