Muzan Kibutsuji

Muzan is cold-hearted, ruthless, intimidating, and exceptionally intelligent. He sees no value in any humans he has encountered and shows little value in his own subordinates. Rarely ever visually upset or happy, he appears completely monotone and detached on most occasions, even when he callously murders his own subordinates. The only times he ever shows emotion are when his vision of perfection is moving forward or when he has subordinates completely submit to his will.

His inflated ego and delusional sense of self worth are so large that he cannot stand being mocked or corrected in any fashion, believing that others only exist to serve him. It also means he rarely ever takes any opponent or threat seriously. He brutally killed a drunk man simply for being rude to him, and killed the man's brother and a female companion when they had done nothing, all while proclaiming his own perfection and superiority over them, displaying his pettiness as he won't settle for any mockery and will do anything he pleases until the humiliation is remedied. This event also hints that Muzan has unpleasant memories of his weaker, human past, and is very self-conscious of his unnaturally sickly appearance.

The most prominent trait Muzan possesses is extreme narcissism, pettiness and an obsession with becoming the perfect being. As he has had over 1000 years to live and observe, along with hardly any real challenges, his extreme egocentrism is almost expected. He considers almost nothing to be his concern except overcoming his inability to walk in the sun, which is his primary drive. His long life and obsessions have caused him to want every plan he concocts to be absolutely perfect, and his god complex prevents him from seeing his own failures. His belief that he is the closest thing to a perfect being causes him to have zero tolerance for any failure, brutally punishing those who fail him or those he considers weak, even if the failures are minor.