Who is Aquaman's arch enemy?

A would-be conqueror of Atlantis from the surface world, the murderer of Aquaman's infant son, Arthur Curry Jr. and Aquaman's deadliest enemy. Broadside: Aquaman vol. 8 #16 (November 2016) An operative of the Nautical Enforcement of Macrocosmic Order organizations wetworks division. read more

Ocean Master: Aquaman's secondary archenemy and half-brother who plots to take over the Throne of Atlantis and destroy the surface world. Black Manta: Aquaman's primary archenemy. Primarily being a mercenary, Black Manta killed Aquaman's son. In a fit of revenge, Aquaman murdered Black Manta's father. read more

Well, technically, they're the same thing. But I suppose you could say that an arch enemy is a forever enemy, as an enemy may just be your enemy for a few days. read more