Demon Slayer: Kimetsu no Yaiba’s main antagonist, Muzan Kibutsuji, who is also the progenitor of all the demons, is the most powerful being with the only weakness of the sun.
He’s also searching for Blue Spider Lilly, which was the main ingredient of the medicine, created by the doctor who treated Muzan’s terminal disease.
Muzan often sends his minions to find the whereabouts of this unique flower in hopes of conquering his weakness over sunlight. Muzan has special control over the demons he created with his blood, with which he could see their memories and can read their thoughts.
Every Demon in the Demon Slayer respects the demon lord because of the fear he inflicts.
Even Upper-Rank Three: Akaza got thrashed boasting about executing a Hashira, insignificant to Muzan as humans are frivolity in front of demons. Apart from that, Muzan doesn’t hate Akaza because of his obedience.
The only Demon he despises the most is the Upper Rank Two: Doma. It is quite a shocker that the second most potent Demon in the Demon Slayer is not Muzan's favorite.
Is Doma not afraid of Muzan in Demon Slayer?
Upper-Rank Two: Doma is a nihilistic maniac and a misanthropic cold-blooded demon. He admits that even when he was human, the term "emotion" was harder for him to comprehend. Doma often hides his true intentions behind the veil of a soft-spoken, humble, and friendly personality.
During the meeting held in the aftermath of Upper-Rank Six: Gyutaro and Daki’s death, Muzan rained his infuriated demeanor upon him for his inefficiency of not finding the Blue Spider Lily and incapable of annihilating Demon Slayer Corps.
Despite panicking and being apologetic towards Muzan about how the rest of the Upper-Ranks would act, he gives an unconcerned disposition like he's not afraid. The only reason why Muzan hates Doma is because of his insincerity and lack of emotions.
This might sound odd, expecting emotions from a demon, but even a demon has to retain such tendencies to keep things in order. Doma primarily targets female humans because of his subjective belief in saving them from misery, contrary to Akaza, who only devours the male humans.
Surprisingly Inosuke’s mother Kotoha Hashibira was killed by Doma, and in her last moments, she threw Inosuke off the cliff into the river, hoping he would survive and live a good life.
The Flower Hashira: Kanae Kocho was killed by Doma and got almost devoured by him. But the daybreak made him leave her. Later, Kanae reveals all the information regarding the Demon, so she would know how to end Doma when the time comes.