Ryomen Sukuna

When Sukuna manifests using Yuji's body, he retains the boy's physical base, but with noticeable transformations that make him appear to be a completely different entity:

Hair: Like Yuji, it is short and messy, light pink in color, although under Sukuna's influence it appears darker or with a reddish tone.

Eyes: His eyes change drastically—they become intensely red, with elongated pupils and a piercing, malicious gaze. Sometimes a second pair of eyes appears on his face, just below the main one, giving him an inhuman and terrifying appearance.

Black marks: This is the most distinctive feature. He has tattoos or black marks running across his body and face.

Two thick black lines cross his nose and cheeks symmetrically.

On his torso and arms, wavy, tribal patterns extend, similar to ancient cursed inscriptions.

Sometimes these marks glow slightly when you use cursed energy.

Extra Mouth: When he takes full control, a mouth sometimes appears on his cheek or abdomen and a little on each hand he has, although they are in the palms of his hands, which he uses to talk or laugh in a disturbing way.

Expression: His smile is mocking, confident, and cruel, with a constant look of superiority. Even when still, he conveys a sense of absolute danger.

Sadistic and cruel: He enjoys the suffering of others; he feels no empathy or compassion for anyone. He delights in violence and destruction, considering them a form of entertainment.

Arrogant and proud: He sees himself as a deity or a superior power. He despises humans, curses, and even the most powerful sorcerers, treating them as mere playthings.

Manipulator: Although he tends to act impulsively, he's also very intelligent and calculating. He likes to play on the emotions and weaknesses of others.

Ruthless: He knows no loyalty or sense of justice. He acts only for his own pleasure or benefit, regardless of the consequences.

Coldly charismatic: Despite his brutal nature, he has an imposing and dominant aura that inspires fear and respect. His manner of speaking is authoritarian and haughty.

Ambitious and destructive: his only interest is to regain his full power and rule the world under his will.

In short, Sukuna represents pure evil, but with an intelligence and pride that make him much more fearsome than a simple monster.