Demon Slayer: Who Is The Weakest Hashira & Why Doesn't It Matter?
In the world of "Demon Slayer," the top-ranking members of the eponymous Demon Slayer Core are known as "Hashira," a title granted to incredibly skilled warriors who have mastered one of the elemental Breathing Styles used by the Core and proved their worth by slaying powerful demons. Each Hashira has a distinctive set of abilities that is usually tied to the unique nature of their breathing style, and although they all share the same rank, some Hashira are far stronger than others.
For example, the Stone Pillar Gyomei Himejima and the Sound Pillar Tengen Uzui both rank in the upper echelon of strength, while the Serpent Pillar Obanai Iguro is shown to be somewhat weak. But the weakest Hashira in the entire series by far is the Insect Pillar, Shinobu Kocho, who canonically lacks the strength to slice off a demon's head. Fortunately, this doesn't really matter, since the unique powers of Shinobu's Insect Breathing Style make her one of the most deadly fighters in the entire Demon Slayer Core.
Within both the manga and anime, Shinobu is shown to rely on quick thrusting and piercing attacks rather than straightforward slashes since her small arms don't allow her to slice through a demon's neck. She uses her Nichirin Sword like an insect's stinger to inject her foes with a wisteria-based poison that is lethal to demons and is able to take down immensely powerful foes with just a single thrust.
Shinobu Kochu is still able to go toe-to-toe with upper rank demons
Contains spoilers for the "Demon Slayer" manga
Despite being physically weak, Shinobu Kochu is still one of the most formidable members of the entire Demon Slayer Core, and she proves as much in the manga's "Infinity Castle" arc near the end of the series.
In the same way that Shinobu Kochu developed an ingenious fighting style to overcome her physical shortcomings, she used her cleverness to outsmart Upper Rank Two, Doma, who is resistant to all of her normal poisons. Shinobu prepared for her fight with the Upper Ranks for more than a year, constantly ingesting a carefully concocted wisteria poison to absorb it into her blood and kill any demon that would be foolish enough to eat her.
Knowing that she lacked the physical strength to beat someone like Doma (the second-strongest demon surviving under Muzan Kibutsuji), Shinobu allowed herself to be eaten by Doma to weaken him and allow a killing blow. This particular poison was so powerful that it actually melted Doma's flesh off of his body despite his poison resistance and healing factor, further proving that Shinobu's skill with toxins made her a match for any demon out there. Although Shinobu may be the physically weakest Hashira in "Demon Slayer," she more than makes up for that weakness with the incredible strength of the poison she creates.