Nezuko is one of the most favorite characters in Demon Slayer Kimetsu no Yaiba anime and manga series, and with episode 7, dubbed Transformation, she sent a serious chunk of the fandom into a fan trance when the audience witnessed one of the most mind-blowing transformations since she became a demon. We are also hooked to Nezuko’s cuteness whenever she is recalling her human life and shrinking to fill the box that Tanjiro is carrying around with her inside.
After seeing how badass Nezuko can be against an Upper Six demon, Daki, who is also one of the Twelve Kizuki demons, and one of Muzan’s favorite. Twelve Kizuki are also known as Twelve Upper Moons, while Daki is Upper Moon Six. The twelve of the strongest demons find their strength in Muzan’s blood. Muzan gave them his blood to make them stronger, while there are also Lower Rank demons. Muzan, of course, controls all demons, and he retains the right to kill them and replace any of the Twelve Kizuki if that pleases him.
As we know, Nezuko is only one of two demons that managed to escape Muzan’s control, which is why he ordered Daki to kill Nezuko, even though he couldn’t possibly know that Nezuko will come to Daki herself with Tengen Uzui, Tanjiro, and the young Demon Slayers. It seems that Muzan already knows that Nezuko’s ability to escape his control can pose a major threat to him in the future. The fandom could also see how Nezuko may be considered a threat to other demons. One of such indicators is her Blood Demon Art she used against Daki.
This Blood Demon Art is designed to hurt only demons and disable their ability to regenerate quickly. Also, given the fact that Nezuko is still a young demon and does not consume or kill humans, she would naturally be weak, which isn’t the case with her. Moreover, her ability to regenerate faster than an Upper Six demon such as Daki, is not a characteristic that can be attributed to Lower rank demons and young demons.