Katsuki Bakugo, raised alongside Izuku Midoriya, earned childhood notoriety for confidence and natural talent, fostering arrogance. He relentlessly bullied the Quirkless Izuku, dubbing him "Deku" and reacting with hostility to any perceived pity, such as Izuku's offer of help after a fall. This behavior intensified at Aldera Junior High, where Katsuki threatened Izuku against applying to U.A. High and destroyed his hero notebook. His Explosion Quirk generates nitroglycerin-like sweat from his palms for detonation, enabling attacks, propulsion, and defense, though overuse strains his arms and shoulders. Achieving top combat points but zero rescue points in the U.A. Entrance Exam reflected his initial victory-over-heroism focus. He raged upon learning Izuku gained admission with a newfound Quirk. Katsuki's volatile personality persisted at U.A., marked by aggressive competitiveness, vulgarity, and dismissive nicknames. Early incidents like disregarding teamwork in the Battle Trial and excessively attacking Izuku highlighted poor cooperation. Defeats, including losses to Izuku and failing the Provisional Hero License Exam due to his demeanor, forced introspection. He gradually acknowledged strategic weaknesses, such as after observing Shoto Todoroki's power during the U.A. Sports Festival, though rarely admitting faults openly. Significant trauma followed his kidnapping by the League of Villains, leading to All Might's retirement. Consumed by guilt, Katsuki confronted Izuku, deduced the truth about One For All, and fought him to process his emotions. All Might later absolved him of blame and shared deeper secrets, forging a confidential bond between the three. This marked the start of Katsuki's reluctant alliance with Izuku, evolving into a rivalry pushing both to improve. Internships under Best Jeanist and Endeavor shaped his development. Best Jeanist modified his appearance and costume for less intimidation, though Katsuki resisted. During missions like the Otheon operation, he utilized specialized stealth gear. His combat skills advanced through collaborations, notably temporarily inheriting One For All from Izuku in the Heroes Rising movie to defeat Nine, showcasing unprecedented teamwork and sacrifice. OVAs provided additional growth contexts. In Training of the Dead, he led classmates against zombies, demonstrating tactical ingenuity. During the remedial license course, advising a child with similar aggression revealed matured self-awareness: "If you keep looking down on everyone, then you won’t notice your own weaknesses". The Paranormal Liberation War proved pivotal. Katsuki intercepted a fatal attack intended for Izuku, sustaining critical injuries leaving lasting scars. Later, during the "Dark Hero" arc, he located Izuku and delivered a profound apology, confessing his past bullying stemmed from insecurity over Izuku's innate heroism. He acknowledged Izuku's worthiness of One For All. In the Final War against All For One and Tomura Shigaraki, Katsuki died from a chest injury but was revived by Edgeshot's sacrifice. Returning to battle with support gear from All Might, he helped defeat All For One and assisted in Tomura's downfall. Post-war, he underwent extensive rehabilitation for his heavily damaged right arm, eventually regaining mobility. Eight years post-graduation, Katsuki ranked among the top-five Pro Heroes as "Dynamight." His costume retained core elements like grenade-shaped bracers—now streamlined—and added fuse-like braids. He funded a powered suit enabling Izuku's continued hero work. Katsuki's appearance evolved from a spiky-haired teenager with a loose uniform to a taller, more muscular adult. Costume variations included winter jackets for optimal sweat production and mission-specific designs like the all-black Otheon stealth suit. Scars from battles, including facial stitches and arm injuries, remained visible. Personality-wise, he retained core traits like competitiveness and bluntness but developed greater respect for allies, leadership accountability, and silent self-reflection. His relationship with Izuku shifted from antagonism to a fierce, mutually-driven rivalry underpinned by hard-earned trust and shared goals.