Worst and unintentionally funniest scene
Easily Black Manta, who had done very little all movie, trying to tell Aquaman why he was the mastermind behind Orm, awkwardly saying "frankly, he irks the sheet out of me" (the swearing felt sooo out of place given how simplistic the movie was), then being eaten by a shark that defied the laws of physics.
Seriously, how did that shark manage to leap straight in the air and scoop up Black Manta without hurling itself out of the water? That was so poorly executed.