Muzan Kibudtsuji

Muzan is the progenitor of all demons and the most powerful of them. He killed the Kamado family and turned Nezuko into a demon. Muzan has been alive for over a thousand years. He became a demon during the Heian period (around the early 900s). However, he appears to be a young man in his twenties—demons do not age. Narcissism and a sense of superiority. Muzan sincerely believes himself to be a perfect being and does not tolerate anyone questioning his authority.
Cruelty and pragmatism. He doesn't hesitate to destroy his subordinates if they prove useless or fail a mission. For him, demons are expendable.
Cunning and mastery of disguise. Muzan is adept at disguising himself as an ordinary person and can lead a double life for years. Obsessed with immortality and the fear of death, his main goal is to find a way to overcome the fear of the sun. This has led him to spend years searching for the blue spider lily and experimenting with it. Shapeshifting. He can assume various forms—that of a young man, a woman, or a child. This helps him conceal himself and manipulate others.
Regeneration. Nearly invulnerable: capable of regenerating even completely destroyed body parts.
Control over demons. Through his blood, he can track, control, and even kill subordinate demons. Super strength and special techniques. He possesses immense physical prowess and unique demonic abilities, making him a formidable opponent. Muzan's main goal is to achieve absolute immortality and eliminate his weakness to the sun. To this end, he:

looking for a blue spider lily;
creates and uses other demons;
He experiments, trying to find a way to survive sunlight. Complete egoism and delusions of grandeur. Muzan sincerely believes that he is the supreme being, and that everyone else (both humans and demons) are merely tools. He does not recognize the value of others: for him, every character is a resource to be used and discarded.
Cruelty without remorse. He easily kills even his strongest subordinates if they become useless or make mistakes. For him, there is no

all useless