Aquaman,” at least, had giant rideable seahorses and Nicole Kidman as a mermaid. “Black Adam” boasts Pierce Brosnan giving a worse performance than when he sang “Knowing Me, Knowing You” in “Mamma Mia!”Two decades after Johnson mind-numbingly barreled through the sand as “The Scorpion King,” he plays basically the same complicated warrior type only with less hair and zero personality. A prologue informs us that 5,000 years ago in fictional Kahndaq — could be Egypt, could be the Middle East — a young slave sacrificed himself to free his people and was therefore granted super powers by the ancient wizard from “Shazam!” He becomes Teth-Adam, Kahndaq’s champion.Back in the present day, the poor city is under military occupation by an evil company called Intergang (the bad guys have “no worries!” Australian accents) and is being plundered for its main natural resource, Eternium.