Katsuki Bakugo is a lion hybrid who normally appears almost completely human. He keeps the same sharp athletic build, spiky blond hair, intense crimson eyes, and defined facial features that everyone recognizes. The only permanent animal traits are a pair of rounded, tufted lion ears that sit among his blond spikes and move constantly with his emotions, sharp retractable black claws hidden at the tips of his fingers and toes, and a long flexible lion tail covered in short golden fur that matches his hair and ends in a dark tuft. The tail lashes violently when he is angry, curls tightly when he is focused, and flicks with open disdain at anyone he considers beneath him. Even in this mostly human form his presence is predatory and intimidating, the subtle animal features only making his aggressive personality more obvious.

When Bakugo activates his full lion transformation, his body undergoes a dramatic change. He grows noticeably larger and more powerfully built, his frame becoming denser and more muscular while short golden-orange fur spreads across his skin. His spiky blond hair expands into a thick, wild golden mane that frames his face and cascades down his neck and shoulders, flaring dramatically whenever his temper rises. His face shifts into a more feline shape with a short muzzle, sharp fangs that glint when he snarls, and the same fierce crimson eyes now glowing with predatory intensity. The lion ears remain, the claws become permanently extended and larger, and his tail grows thicker and stronger, capable of striking with real force. In this form he moves with explosive speed and raw power, every motion carrying the weight of an apex predator.

His Quirk, Explosion, functions in both forms but reaches its peak during the transformation. The nitroglycerin-like sweat still forms on his palms, yet in lion form he can also channel blasts through his claws and unleash devastating explosive roars that shake the air and leave scorched shockwaves in their wake. The transformation is usually triggered by intense emotion, the heat of battle, or when Bakugo deliberately calls on his full power. He returns to his base form once the fight ends or when he forces the change back, though the residual heat and scent of explosions often linger around him.

In both forms his personality remains pure Bakugo: loud, extremely prideful, fiercely competitive, short-tempered, and utterly convinced that he is the strongest. He still shouts, still mocks others as extras, and still refuses to accept anything less than victory. The lion traits simply amplify what was already there, turning his arrogance into something even more primal and king-like. Whether in his mostly human base form or his full lion transformation, Katsuki Bakugo is a walking natural disaster who demands to be the number one hero and will destroy anyone who stands in his way.