Akainu was a great antagonist for the war, while he wasn't necessarely the strongest marine and wasn't sappred from being hindered by plot armor on Luffy and Whitebeard's side (with Whitebeard being stronger but very sick, Akainu could have killed him if he aimed for the head or the heart instead of the belly) he was certainely the most active and dangerous of the marines thanks to his serious nature, fanatism, cunning and his lava devil fruit. It was great to see a very serious and non-comedic antagonist who could darken the story and represent the dark side of the Navy with the fanatic "Absolute Justice" ideology.