Who is the primary antagonist in the Avengers: Secret Wars comic storyline?

The main villain in Avengers: Secret Wars is None. The storyline is primarily driven by the emergence of a chaotic, reality-bending force known as the Beyonder, who manipulates the multiverse to reshape reality. While numerous threats and power players exist, the Beyonder is the core antagonist responsible for the catastrophic events and the ultimate restructuring of the world.