Initially, Tanjiro's accuracy and strength were not up to the mark, which is why Muzan was able to avoid his attacks. However, Tanjiro accurately performed the thirteenth form and inflicted a ton of damage on the Demon King.
The Thirteenth Form of the Sun Breathing Style is unique in the sense that it doesn't really have a name of its own. Rather, it's a combination of all the twelve forms present in this style, used in succession to maximize their power. This move was devised by Tanjiro solely to defeat Muzan.
Thirteenth Form of Sun Breathing in Demon Slayer
This technique's primary purpose is to slash all the twelve vital organs of a demon. Each form targets a specific organ. Tanjiro only used it once in the manga.
Since you're reading the manga anyway, I'll tell you what the 13th form actually is. It's revealed in chapter 192. Basically, up until now, Tanjiro's movements in the Hinokami Kagura have been very rough and overall pretty "barbaric", I guess you could say. Like when a white belt at Tae-Kwon-Do performs a kick wrong.
13th form Tanjiro simply blitzes Akaza. In that form, he's relative to WH Muzan in speed who is faster than all the UMs.
Unmarked Giyu did better against Akaza than Marked Tanjiro did (without Transparent World or Selfess State yet). Considering Unmarked Sanemi is on par with Unmarked Giyu, Unmarked Sanemi would definitely win against Marked Tanjiro.
However, the thirteenth form is the one that would land the final blow on Muzan. This form is a repetition of every Sun Breathing form performed in succession that would kill Muzan by hurting all of his vital organs.
This anime repeatedly shows viewers the clear difference in the strengths of demons and humans, and that teamwork is the only way to overcome a task that seems insurmountable. In conclusion, Tanjiro will not be able to kill Muzan by himself since the Demon King is far superior in every aspect of combat.
But if we are talking about the human form, then it's a big fat NO, because Tanjiro has just mastered the Sun Breathing whereas Yoriichi is the inventor of it, also he's way more powerful and holds an unfathomable battle intellect, larger than any Demon Slayer in history, so in conclusion, no one is remotely close to ...
Moon Breathing is the demonic form of the primal Sun Breathing in Demon Slayer anime and manga. Developed by Kokushibo, aka Michikatsu Tsugikuni, this is the second most powerful breathing technique in the series that no human can use. Moreover, it also has more forms than any other type of breathing.
"Breath of the Sun: Thirteenth Style") is the thirteenth form the Sun Breathing and the pinnacle of all Breathing techniques in history. This technique was created by Yoriichi Tsugikuni himself in order defeat Muzan Kibutsuji.
We see Tanjiro using 13 Form quite literally wrecking Muzan better than all Hashiras did together.
Tanjiro Gets Reincarnated Into A Happy Family.
Overall Abilities: Despite not being a Demon Slayer and having a tragic disease that makes his body incredibly frail, Tanjuro was shown to be a phenomenally strong individual. He was able to slay a bear nearly nine feet tall with a single axe at speeds magnitudes faster than the blink of an eye.
Many Kimetsu no Yaiba fans deduce that Yoriichi is Tanjiro's father, but that isn't the case. However, Yoriichi is responsible for teaching Tanjiro's ancestors the Hinokami Kagura, which has been passed down for generations.
Is upper rank one Tanjiro's father? No, they are not related. Tanjiro, by PURE COINCIDENCE, heavily resembles Yoriichi Tsugikuni, the creator of Breath swordsmanship, the only other person to use Sun Breathing, and the only person Muzan ever feared.
Yoriichi lived till old age, likely due to him having been born with the mark and thereby avoiding the curse altogether. Gyomei on the other hand did not activate his Mark until he was already older than 25. It was speculated that when he awoke his Mark during battle that he would likely die within hours.
1 Gyomei Himejima - The Stone Hashira
The oldest of the bunch, the Stone Hashira, Gyomei Himejima is 27 years old.
Despite the intensity of his battle against the demon, he never manifested his Demon Slayer Mark, and undoubtedly did not even know the conditions for doing so.
Seventh Form: Flaming Thunder God) - The personal creation of Zenitsu Agatsuma. The user dashes forward at blinding speeds and unleashes a singular forward slash at a low stance, which is seemingly accompanied by a yellow Japanese dragon shaped like a lightning bolt.
Sun Breathing was initially created with 12 techniques all connected to one another by Yoriichi Tsugikuni. Later upon meeting Muzan Kibutsuji, Yoriichi perfected his swordsmanship form, creating a new unnamed thirteenth form.
1 Muzan (Demon Slayer)
Without that antidote, it would have been impossible to kill him. So despite all her strength and humanity, Nezuko would have easily lost to Muzan.