1) Shinobu Kocho The Insect Pillar of Demon Slayer Corps, Shinobu is undeniably the smartest individual.
Apart from that, Shinobu is a great mentor as well. 14-year-old Muichiro Tokito ranks second on the list of most intelligent Hashira followed up by the strongest Hashira Gyomei Himejima in third place.
The Insect Pillar of Demon Slayer Corps, Shinobu is undeniably the smartest individual. She might not be physically stronger than others, but her intelligence is what kept her going. Shinobu is proficient in medical knowledge and can also create poisons out of wisteria flowers that are lethal to demons.
Yoriichi Tsukiguni is arguably one of the smartest members of the Demon Slayer Corps in terms of battle intellect. He was a prodigy in combat, and there isn't a single character in the series who could match what he has been able to achieve.
Keen Intellect: Shinobu possesses vast knowledge in using poison in combat. She has one of the best IQ in the Corps, having an IQ of over 200 making her a genius.
Shinobu and her older sister Kanae were from a wealthy family who worked in compounding medicine but their life was ruined when a Demon attacked their home killing their parents.
Giyu points out that Shinobu can't stand cats, dogs, and pretty much any animal with fur, although she denies it. According to Shinobu, the first one among them to speak gets to greet the Master, Kagaya Ubuyashiki, so they all had butterflies in their stomachs until their Master arrived.
Tengen Uzui
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.
Kim Ung-Yong
He holds the Guinness World Record for IQ at 210 and he was invited as a guest student in physics at Hanyang University when he was three year old. He was invited to America by NASA at age eight, he worked at the space organization for ten years and then returned to Korea.
Tamayo is arguably one of the smartest characters in Demon Slayer since she is one of the major reasons why Muzan died to the members of the Demon Slayer Corps.
Shinobu holds a strong resentment and hatred for Doma, due to him killing her older sister, Kanae.
GiyuShino is the het ship between Shinobu Kocho and Giyuu Tomioka from the Demon Slayer fandom.
5/14 Fastest Hashira In Running
Despite his large and muscular build, Tengen Uzui is the fastest runner among the Hashira.
But, when it comes to who was the better Hashira, Tengen wins by a considerable margin. His experiences as a shinobi and as a Demon Slayer far exceeded Rengoku's, and led to him developing far superior strength, battle tactics, and techniques.
Adragon De Mello: IQ 400
In 1988, when Adragon De Mello graduated from the University of California, Santa Cruz, with a degree in computational mathematics at the age of 11, he was the youngest college graduate in the United States (a record he no longer holds).
William James Sidis has the World's Highest IQ. Anywhere from 250 to 300 is his IQ score, almost twice the score of Albert Einstein. At the age of eleven, William famously entered Harvard University, becoming the youngest person to enter.
2) Sanemi Shinazugawa
His fast movement, combined with his excellent swordsmanship, makes him a remarkable demon slayer. Most of his attacks are purely offensive due to his breathing style. Being a user of wind breathing, he is undoubtedly fast.
Zenitsu is at least close to Hashira level by the end and Godspeed has limited uses because it disables his legs after those uses. Zenitsu's faster but if this was an actual race or marathon, Shinobu would beat him.
When it comes to pure strength, Shinobu Kocho is the weakest Hashira in Demon Slayer. She doesn't even have enough strength to decapitate a demon's head and she makes up for it by injecting poison into the demons.
In her inital appearance, Shinobu was completely mute, not speaking at all, except for a few occasions. Even so, she is normally very talkative, and could not stand being silent for more than a few months. She has a haughty and arrogant demeanor, being very prideful and overly confident in her own abilities.
After the death of Kanae, however, Shinobu began to outwardly behave more like her sister and eventually developed her positive attitude and mannerisms to match while internally holding in her rage, which she later clarifies is fueled by her desire to continuously display the smile that her sister favored.
However, her playful attitude is revealed to be fake—in reality, Shinobu holds a deep, intense hatred for demons due to almost all of her loved ones (her sister, her parents, and almost all of her tsuguko) being killed by them, so much so that she is in a near-constant state of anger.