Akaza is one of the 12 Kizuki, the strongest demons who serve directly under Muzan Kibutsuji in Demon Slayer. He is Upper Rank 3, making him particularly powerful. The Upper Ranks went 100 years without being killed by a Hashira, while killing a large number of Hashira themselves.
When Kyojuro Rengoku encountered Akaza, he knew that fighting an Upper Rank meant nothing but death. Akaza has incredible strength and speed, as well as Blood Demon Arts that can find a target's weak points and create dozens of shockwaves from successive hits. At this point in the manga, the Hashira had yet to gain their marks, and were later required to team up in order to kill the Upper Ranks. Fighting one-on-one against Akaza for very long would have been nearly impossible for any Hashira, but some could have lasted until sunrise.
8 Would Win: Shinobu Kocho Has A Variety Of Poisons
Shinobu may not have the strength to cut off a demon's head, but she is still a powerful and capable fighter. She is the fastest of all of the Hashira, which is important to keep up with Akaza, someone who moved too quickly for Tanjiro's eyes to follow. Rather than relying on sheer force, she has created a variety of poisons made from Wisteria flowers. Over time, she can discern how much poison and what mix of poison would be most effective against her opponent. On her own, she drastically weakened Doma, Upper Rank 2. Against Akaza, she would have a better advantage if she was able to hinder his ability to heal at fast speeds.
7 Would Lose: Giyu Tomoka Needed Tanjiro To Win Against Akaza
During the Infinity Castle Arc, Giyu had to fight Akaza with Tanjiro. Akaza was able to match Giyu's speed even after Giyu manifested his own mark. Without Tanjiro, Giyu never would have managed to win. Akaza was powerful enough to destroy Giyu's sword, which is his primary weapon. It is thanks to Tanjiro's presence there that the two swordsmen were able to pull off a win against the demon, but they lose consciousness soon after.
6 Would Win: Gyomei Himejima Is Currently The Strongest Demon Slayer
Even before becoming a demon slayer, Gyomei was immensely powerful. He was able to defeat a demon with his bare hands, keeping it down with repeated punches until sunrise. He grew his strength and stamina by utilizing repetitive motions, sitting under waterfalls and pushing boulders far larger than himself.
All of the other demon slayers acknowledge him as the strongest, and he was able to survive fights against Kokushibo, Upper Rank 1 among the 12 Kizuki, and even Muzan.
5 Would Lose: Mitsuri Kanroji Couldn't Defeat Upper Rank 4 By Herself
Mitsuri was always powerful, capable of lifting things twice her weight since she was a child. She wields a unique whip-like sword that can only be used by her, due to her flexibility and the composition of her muscles. Although she is able to attack from a distance, Akaza has proven himself eager and capable of closing the distance between himself and his opponents. While Mitsuri can withstand an attack from an Upper Rank, given the unique structure of her body, she wouldn't outlast Akaza, especially considering she wasn't able to defeat Upper Rank 4, Hantengu, on her own.
4 Would Win: Sanemi Shinazugawa Makes Demons Drunk Off His Blood
Sanemi is the second-strongest Hashira of the current generation. His swordsmanship managed to impress Kokushibo. He has a rare blood type, which smells so intoxicating to demons that it makes them drunk if they catch a whiff of it. It affects even the strongest of the Upper Rank demons.
This would be effective against Akaza because the only people he refuses to eat are women, since that goes against his morals. Sanemi also has excellent control of his muscles, saving himself from fatal injuries by closing them up himself. This allows him to continue fighting when most others would succumb to their injuries.
3 Would Lose: Obanai Iguro Is One Of The Hashira's Weakest Members
Obanai is considered to be one of the weakest members of the Hashira, like Shinobu. Since he is partially blind in one eye, he relies on his snake to guide him in battle, which is so effective that it's a viable strategy even when he's completely blind. However, this makes his snake a weak point for him. He has the same amount of determination and is a master swordsman like the other Hashira, but he doesn't have the physical strength needed to match Akaza's.
2 Would Win: Muichiro Tokito Can Manipulate The Senses Of His Opponents
Despite losing his limbs and suffering from other fatal wounds, Muichiro is still able to fight for a long time, attesting to his incredible endurance and willpower. Muichiro has defeated Upper Rank 5 by himself, although Kotetsu's assistance helped him to break out of the water prison. His mist-based techniques and his loosely fitting clothes make it difficult to tell what he is about to do, which gives him a terrific advantage against his opponents. He is also strong enough to behead an Upper Rank in a flash.
1 Would Lose: Tengen Uzui Can't Counter Akaza's Compass Needle
Tengen received training as both a ninja and a swordsman. This not only strengthened him, but also sharpened his senses so that he can attack with more accuracy. By utilizing sound, he can predict the movements of his opponents. He would be disoriented by the shockwaves created by Akaza's blows. Tengen has anti-demon bombs that can disorient them for a short period of time, but this wouldn't be an effective strategy when Akaza uses Compass Needle, which allows him to accurately pinpoint and aim for his opponent's weak spots.