The film begins with an in-depth look at the early life of a famous boxer, showcasing his rough upbringing in Brooklyn, New York. Facing numerous challenges, he finds solace in boxing, which eventually leads him to train under Cus D'Amato, a legendary boxing manager and trainer. The relationship with Cus proves to be transformative, as the young athlete develops his skills and enters the professional boxing world, rapidly rising through the ranks due to his raw talent and fierce determination. The combination of his natural ability and rigorous training culminates in a meteoric rise to fame, where he becomes the youngest heavyweight champion in history.

As his fame grows, so do the pressures and challenges outside the ring. The film delves into his struggles with personal demons, legal issues, and turbulent relationships. The pressures of life in the spotlight begin to take their toll, leading to a series of controversial incidents that overshadow his achievements in the sport. His career faces numerous ups and downs as he attempts to navigate his personal and professional life amid rising scrutiny. The story paints a detailed picture of the dichotomy between his powerful persona in the ring and the troubled individual grappling with personal challenges behind the scenes.