Shinobu Kocho is a capable Demon Slayer whose worthy of being the Insect Hashira. That being said, she's arguably the weakest Hashira when it comes to pure strength.
1) Gyomei. Gyomei Himejima is the strongest Hashira in Demon Slayer. This fact has been established in the manga as Tanjiro, Inosuke and Zenitsu all agree that he is the strongest member of the Demon Slayer Corps.
Giyu Tomioka was the first Hashira introduced to the series, and is easy to name among the strongest. In addition to how easily Giyu defeated Rui when Tanjiro struggled against him, Demon Slayer's Giyu Tomioka was able to put up a great fight against Akaza, although he never managed to have the advantage over him.
He is the fastest Hashira, and the second physically strongest. Obviously, then, Tengen Uzui is rather proud. He is demanding, fussy, boastful, and prone to selfishness. But he is also ultimately kind and caring, with great love for his three wives as well as the other Hashira.
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.
Obanai Iguro is one of the harsher Hashira members. He demanded that Giyuu be punished for allowing Nezuko to get away unharmed, and later restrained Tanjiro as he tried to help his sister. He hates demons and has little regard for his fellow Hashira, except Mitsuri Kanroji later on.
After awakening his demon slayer mark, Giyu greatly overpowers Akaza. However, he is able to keep up with the fight only because of Tanjiro. If Giyu had soloed against Akaza, he would have died.
Tanjiro decapitates Akaza with the Hinokami Kagura: Setting Sun Transformation. Akaza was bewildered, wondering how Tanjiro did not have any fighting spirit, comparing this feeling to fighting against a plant. He acknowledges that Tanjiro surpassed his speed.
5 Hashiras who die in Demon Slayer, and how it happens.
Rengoku's Unwavering Will Was His Greatest Weakness
Since he believes it is his responsibility as someone strong to protect those weaker than him, he will make sure he does just that. Rengoku sees any mission through to the very end, even at the cost of his life.
In terms of physical strength, Tengen Uzui is far from being the weakest Hashira. While his feats throughout the Daki and Gyutaro battles certainly displayed this, there's additional evidence to show that he's not the weakest Hashira.
14 She Has A Really Sweet Relationship With The Hashira Mitsuri Kanroji. In the manga, Nezuko gets to know the Love Hashira Mitsuri Kanroji and looks up to her like an older sister, which makes their relationship interesting since Nezuko usually sees female humans as either a surrogate mother or a young sister.
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.
1 Muzan Kibutsuji
The Demon King Muzan Kibutsuji has seven hearts and five brains, making him one of the most intelligent characters in the Demon Slayer anime series.
The flashback also reveals that Yoriichi had a twin brother named Michikatsu Tsugikuni, who became a Demon Slayer but later turned into a demon and became Upper Moon One, Kokushibo.
Moreover, Tanjiro's appearance somewhat resembled Tsugikuni. So the only reason Muzan is afraid of Tanjiro is because of the Hanafuda earrings he possesses, which acted as a reminder of his downfall.
The demon slayers successfully defeated Muzan.
During this arc, Tengen showed why he's one of the sharpest Hashira in Demon Slayer.
Giyu was the first Hashira to be introduced in the series, making his debut in the very first episode. After rescuing Tanjiro from the newly transformed demon Nezuko, Giyu prepares to execute her as he would any other demon.