Tris begins the novel as someone who has been taught that wanting things is a moral failure, and ends it as someone who has killed for the people she loves. The arc is not a corruption — it's an expansion. She carries Abnegation's selflessness and Dauntless's bravery simultaneously, which makes her Divergent in the most literal sense: she is two things at once, and the system cannot process that. Her central struggle is the right to be complex in a world that punishes complexity.