Who is the antagonist in divergent?

In "Divergent," the primary antagonist is Jeanine Matthews, the leader of the Erudite faction. She seeks to control the factions and eliminate those who do not fit into the societal structure, particularly the Divergent individuals who possess multiple faction traits. Her ambition and ruthless tactics create significant conflict for the protagonist, Tris Prior, and her allies as they fight against her oppressive regime.