1) Giyu Tomioka If Giyu fights Doma, he would lose miserably as the latter is stronger than Akaza and his speed is impeccable. Moreover, water breathing would be a bad technique in front of Doma's Cryokinesis.
Douma is way stronger than Upper Moon Three Akaza whom both Giyuu and Tanjiro couldn't defeat. Douma is way stronger in everyway,speedy and has tricky abilities which I believe would just be too much for both Tanjiro and Giyuu.
Sanemi is inarguably one of the strongest Hashira in Demon Slayer who has the potential to gain victory over Giyu. Both the characters possess immense speed and endurance, and they also can take on an Upper Rank demon head-on.
Gyomei cannot beat Doma on his own..and thats because of Doma's ridiculous abilities..
While Sanemi and Giyu are pretty evenly matched, it's possible Sanemi would win a fight between them based on his ruthless nature alone. Giyu has shown mercy, but Sanemi isn't the type to hold back for any reason.
In terms of overall combat abilities, Iguro is quite close to Giyu Tomioka. However, fans believe that he is stronger than Giyu since he was able to last longer than the other Hashiras during the fight against Muzan.
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.
Most people say that Giyu would win in a fight, but in terms of overall strength, Obanai is considered the 3rd strongest Hashira, followed by Giyu and Muijira. One reason is his unique fighting style, which utilizes a bending sword. and allows his attacks to reach farther.
If Giyu fights Doma, he would lose miserably as the latter is stronger than Akaza and his speed is impeccable. Moreover, water breathing would be a bad technique in front of Doma's Cryokinesis.
The rank alone speaks for itself. Douma (or Doma, idc) is higher than Akaza in overall power and rank among the 12 Kizuki. See, basic thing is rank.
It was still impressive, nonetheless, and even with the injuries he sustained, Giyu managed to contribute a lot in the final fight against Muzan and ended up as one of the few Hashira to survive the fight. All in all, Giyu very clearly stands among the strongest Hashira in the series.
Giyu is one of the legendary Hashira, and he's brought down demons far more powerful than Nezuko. With his level of skill and impressive agility, he'd easily defeat Tanjiro's little sister. In fact, when Giyu first meets Tanjiro and Nezuko, he almost does kill the latter.
Sanemi and Doma may be comparable in terms of power, but if they had to fight, Doma would probably emerge victorious. The reason Doma lost was because of Shinobu's poison that significantly weakened him. This eventually helped Inosuke and Kanao to defeat him.
The only reason Doma couldn't regenerate his head was because he took in poison that would kill a demon 700 times over. And the fact that he got poisoned before doesn't mean he was weaker during the fight, especially since he showed no sign of it and he has regenerative abilities.
Muichiro can defeat Akaza easily with his petite body that leverages his speed. Moreover, his ability of Transparent World can aid him in landing a fatal blow on Akaza's weak spot.
Zenitsu would be the second weakest in the fight and but I think he would keep Doma on his toes since Zenitsu's new form of thunder breathing was pretty fast. Inosuke would probably be the weakest against doma but his double blades would keep the ice particles out like he did in the manga.
Shinobu could fight Giyuu but it is pretty debatable on who would win since they both are strong enough to fight uppermoons, but we have to consider the fact Shinobu lasted against a demon much stronger than Akaza who Giyuu could barely fight.
Obanai Iguro – Serpent Hashira
We see the peak of Obanai's strength when he was able to easily hold off Nakime, the Upper Rank 4, and even got close to beheading Muzan, the demon king. During the Infinity Castle Arc, he killed a bunch of demons who were equivalent to the lower ranks without giving it a second thought.
Sanemi also has great enough control over his muscles to manipulate them into forcing wounds closed and such, a great feat indeed. Finally, his strength and skills are said by Kokushibo to be at their absolute peak, further solidifying Tanjiro's hopeless chances against Sanemi in a fight.
But, comparing the two characters in their best forms, Zenitsu might be just a tad bit faster owing to his Godspeed move.
Rengoku's fight in the Mugen Train arc showed his incredible speed and reflexes. He was able to match Akaza's speed, and his movements were so fast that it was almost impossible for the naked eye to keep up. Tengen, meanwhile, is the fastest runner out of all the Hashira.
Least Favorite: Obanai- he had so much potential, but he was barley used and most of that potential was wasted. The sad backstory wasn't able to redeem him for me, it felt kinda forced to make people like him.