While she might not be as powerful as Muzan himself, her overall strength makes her easily comparable to an Upper rank demon.
Muzan, the King of Demons, is the strongest and also the primal demon in the world of Demon Slayer. Consuming his blood is enough to turn you into a powerful demon. He can control all the demons in existence, with only people with strong willpower like Nezuko being an exception.
Muzan can detect the locations of his demons and can also read their thoughts. However, Nezuko and Tamayo are the only exceptions in the entirety of Demon Slayer, over whom Muzan has no control.
There is no doubt that Nezuko is faster and stronger than the base form of Tanjiro. However, he can activate his Demon Slayer Mark and happens to be a user of the Breath of the Sun. This gives him an edge because it is one of the series' strongest and most efficient breathing techniques.
Muzan had attacked Tanjiro's family and shared his blood with Nezuko.
Secondly, Muzan would probably… eat Nezuko and Tanjiro in the hopes of obtaining their sun-resistance abilities, and also since he wouldn't be able to convince them to become demons to work under him. This would allow him to become the ultimate demon.
The two known demons who broke free of Muzan's curse are Tamayo and Nezuko. Tamayo was able to break free of the condemnation when Yoriichi fought Muzan, nearly killing him in the process. During this weakened state, Yoriichi let Tamayo go, free her from Muzan, and free her from the curse.
In conclusion, Nezuko cannot beat Akaza in Demon Slayer. In terms of power, physical abilities, regeneration rate and overall combat ability, Akaza is far superior compared to Nezuko.
Weakness(es)
Nezuko Kamado, like any other character, has her share of weaknesses that she needs to overcome. One of her main weaknesses is her inability to control her demon instincts at times, leading her to act impulsively and recklessly.
It is theorized that Nezuko was able to conquer the Sun because she comes from a lineage of Sun Breathing users and because she kept a big part of her own humanity i.e. because she never ate human flesh.
While she might not be as powerful as Muzan himself, her overall strength makes her easily comparable to an Upper rank demon.
Since members of the Kamado family have been practicing some form of the Breath of the Sun, Muzan attempted to create the perfect demon by turning Nezuko into one. There was some merit to this strategy since Nezuko was able to develop immunity to sunlight which was featured in the fight against Hantengu.
Muzan spared Nezuko most likely because she expects something from turning a member of the Kamado family. True enough, Nezuko grew and transformed over the series. She demonstrated her Blood Demon Art during the fight with Rui. Nezuko then did her Demon Transformation in the fight against Daki.
However, the trait that sets her apart from all other demons is the fact that she has the ability to conquer the sun, prompting the Demon King to call her the "chosen demon". Abnormal Demon Physiology: As the "chosen demon", Nezuko has several unique demonic traits that set her apart from all other demons.
As the main threat occupying the position of Upper Moon Six, Gyutaro's Blood Demon Art is tremendously powerful and extremely dangerous. With it, he can perform various attacks using blood from different parts of his body, and project them from his sickles as well.
Nezuko's most significant trait, however, is her immense growth, which is likely due to a combination of the amount of blood she received from Muzan and her willpower. To conclude, Nezuko is a formidable powerhouse within the anime and is probably one of the strongest main characters in the series.
1 Exploding Blood/Pyrokinesis Blood Demon Art
By far, this is Nezuko's most damaging technique when it comes to fighting her own kind.
Nezuko, the young sister of the main protagonist Tanjiro, has a special Blood Demon Art called Exploding Blood that allows her to ignite her blood into pink flames and even summon it from thin air. Unlike other demons, Nezuko doesn't consume humans to grow stronger but instead rests to unlock her full potential.
And the Wind Hashira, Sanemi Shinazugawa, draws his sword against Nezuko…
From the beginning of the series, Kibutsuji Muzan was established as the most fearsome demon in existence. He is responsible for the creation of all other demons in the series, of which most are still extremely fearful of him, as he has been shown to slaughter subordinates that displease him.
Ultimately, Nezuko survives and finally turns into a human after being stuck as a demon for so long. Despite turning into a human, she's one of the prime reasons why Tanjiro could defeat Muzan, even after almost being turned into a demon himself. The manga comes to a conclusion after the fight with Muzan.
The warrior Muzan feared was a swordsman named Yoriichi Tsugikuni. Yoriichi was the only slayer before Tanjiro who came close to killing Muzan, and the flashback of their fight occurred in Chapter 187.
Muzan Kibutsuji (鬼舞辻無慘, Kibutsuji Muzan) is the main antagonist of the Demon Slayer: Kimetsu no Yaiba fantasy action manga and anime series. Muzan is the powerful Demon King, who has the ability to inject his victims with blood that allows him to convert them into more demons.
Akaza was also one of Muzan's favorite demons out of all his subordinates. The reason behind this is Akaza's extreme loyalty to his master. The Upper Rank Three demon was always sent away on special missions, something the Upper Rank 1 and 2 were often denied of.