On a September evening in Dublin, Katie Taylor stood before 80,000 of her own people at Croke Park and chose, at the height of her powers, to walk away. She defeated Flora Pili by unanimous decision to claim a fourth world title and retire undefeated as a professional, closing a career that began in defiance of rules that said women could not box at all. What unfolded was less a sporting event than a reckoning with how far one person's refusal to accept limitation can carry an entire generation.