Atlanna preserves her badass mom queen status in this film through going on an epic chase sequence through Atlantis in pursuit of Manta.
At the beginning of the climax, Aquaman reveals all the backup he brought to deal with Manta's sonic cannon, the most devastating weapon that the pirate has in his arsenal: dozens if not hundreds of whales, who he commands to turn their echolocation abilities into their own sonic weapon. This turns out to be so powerful that it doesn't just prevent Manta's crew from firing their own at the Atlantean forces, but so completely outclasses the sonic cannon that it overloads and blows up, disabling the whole submersible superweapon at once.
As Mera is attacking Black Manta's pod, he shoots her with a huge plasma blast that slams her into a rock and leaves her covered in burns and almost unconscious. But as Manta prepares to move in to finish her off, Arthur slams into him and send him flying, shouting, "STAY AWAY FROM MY WIFE!"
As Manta's ship is fleeing Demon's Deep, Arthur tries to chase them but is knocked back by their sonic cannon and almost crushed under rocks falling on him. Cue Mera, returning after last being seen in the hospital, using her hydrokinesis to move the rocks and save him.
And in the Final Battle, Manta has Arthur pinned to the ground and is ready to finish him off, while Junior is still on the altar nearby. Mera makes a Dynamic Entry by slamming him with a blast of water before he can kill her husband.
Orm is starved, regularly beaten, and widely hated by his former subjects while being kept in a Hellhole Prison. Nonetheless, he actually argues against his brother breaking him out of jail (and is willing to turn himself back in) due to not wanting his kingdom to end up at war yet again.
Orm barely survives in prison on a bucket of sea water. Once he reaches a beach shore and gets a wave over his body, he's back in form and saves Arthur.
Orm faces off with an octopus mech, and beats it.
Dr. Shin swapping out Junior with a time bomb that goes off the moment Black Manta opens it, almost killing him in the ensueing explosion after Shin spent most of the movie having his life threatened by David.
The final fight between Arthur and Black Manta with their tridents clashing against one another.
When Manta tosses Kordax's trident at Mera and her baby, Orm catches it, and gets possessed by Kordax as a result. It's a willing Heroic Sacrifice from Orm that he was willing to damn himself to save his rival/brother's baby.
Arthur frees Orm from Kordax by grabbing onto the Trident, gambling losing himself to it, and giving a simple talk to Orm that enables his brother to break free.
Arthur throwing his own trident directly through the Black Trident, causing it to shatter and in turn destroy Kordax. Robin Hood would be proud!
The end of the film. Arthur, Nereus and the Brine King reveal the existence of Atlantis to the world. The three kings standing together facing the surface world is a magnificent moment.
