I don’t recall Atlantis making tsunamis all they did was wash up dirt and battleships.
Wakanda wins round 1 (only royals can breath on land so all the forces will have water pumps which are a major weakspot) hard win
Round 2 Atlantis stomp hard
If they can create waves strong enough to drag warships and 30 years of garbage to coastal cities, it is not easy for them to create a tsunami. Moreover Orm and Nereus only did this as a warning, which means that they could flood the cities