Aquaman is muuuuuuuuch faster, stronger and more durable than Attuma and the Trident seals it.
He can also mindrape Attuma if he is bored with the fight.
PS. Attuma in the (rather disappointing) Avengers Assemble was I've seen, but he still is much slower than Aquaman and susceptible to damage from the Trident, although it would be a better fight, albeit the result would be the same.
@fallschirmjager: One of Namor's major villains.
Underwater barbarian warlord. Super Strength, underwater speed, good fighter and leader, full Atlantean.
He used to be around "class 60" going by Marvel metrics, but I think Doom enhanced him in the past few years.
Still just a generic melee brute kind of character.