Walter Simmons is the secondary antagonist of the 2021 MonsterVerse film Godzilla vs. Kong and the overarching antagonist of the Apple+ television series Monarch: Legacy of Monsters.
He was the powerful CEO of Apex Cybernetics and the father of Maia Simmons. Driven by a need to feed his ambitious ego, Simmons, in the face of the Titans' existence being revealed, sought to be the one to re-establish humanity as the sole "apex" species on Earth with his company on top. To that end, he opts to build Mechagodzilla after getting the psionic skull of Ghidorah's severed left head, masterminding a corporate conspiracy to use the machine to murder the heroic Titan Godzilla and usurp his status as King of the Monsters, after he's allowed his experiments to galvanize Godzilla into rampaging in two cities and threatening millions of people.