While unconscious, Zenitsu is a force to be reckoned with, but his actual power is discovered when he is awake. While awake, Zenitsu was able to match the upper rank six, Kaigaku. He was also able to keep up with the Demon King, though he was in a weakened state during this battle.
But the manga shows that he can fight without fainting or going unconscious. Later in the manga, Zenitsu fights an Upper Moon 6 demon named Kaigaku. He was Zenitsu's senior and wielded the Thunder Breathing Style. During that fight, Zenitsu was conscious the whole time.
Zenitsu is one of the main characters, and he does stop being a coward in Chapter 143–146, which is hte final arc of the series.
There are six forms, but Zenitsu could only learn the first form said to be the basis for the others yet he honed it to where he could fight against several strong demons. He later created a seventh form and defeated his former senior who had become the Upper Rank Six of the Twelve Kizuki.
Episode 12 | Kimetsu no Yaiba Wiki | Fandom.
NO. It's his subconscious mind that helps him fight. When he fainted out, his subconscious mind takes over( something like semi-hypnotic state) and unleashes the lighting breathing. Consciously he is not confident enough.
Tanjiro Is Strong, and Stronger than Zenitsu as he uses Sun Breathing.
Thunder Clap and Flash—Godspeed is the most powerful of Zenitsu's derivations of the Thunder Breathing first-form technique.
Thunder Breathing is one such technique that Zenitsu has used to great effect in the series. Of course, Zenitsu is only the master of the first form, but it goes without saying that the other techniques of Thunder Breathing will also be awe-inspiring to witness in Demon Slayer.
Unfortunately, he retired at the age of 35, when he lost his right leg in a fight with a demon. Since then, he devoted his time to teaching the next generation of demon slayers, most notably, Zenitsu Agatsuma, who lovingly called him "grandpa".
Demon Slayers are known for their strength and bravery in battle, but not Zenitsu. Despite his cowardice, he's one of the strongest in the series.
Zenitsu — Anxiety
To the surprise of absolutely nobody, Zenitsu is anxiety incarnate. He starts out the series so paralyzed by fear that he can't even fight when he's conscious, and so he's only able to fight when he's passed out.
Nezuko Kamado
Zenitsu also protects Nezuko multiple times when she is in danger, evident during Zenitsu's first meeting with Inosuke Hashibira and the battle against Enmu in the train. Eventually Zenitsu and Nezuko would marry and start a family as evidenced by their descendants.
Zenitsu is an easily frightened demon slayer with a powerful secret. When he sleeps, his inhibitions fade away and he becomes so lighting-fast he can draw, swing, and resheath his sword before a demon's head even hits the ground.
The reason for this is pretty simple. Zenitsu wasn't able to master the other 5 forms. He never wanted to learn any breathing techniques. or fighting techniques, nor he wanted to join the Demon Slayer Corps.
After mastering his Thunder Breathing, Zenitsu would eventually become capable of awakening his Demon Slayer Mark. As this mark would enhance his strength and speed, he can overwhelm Gyomei to a certain extent, but he still won't manage to defeat him.
1) Tanjiro Kamado
Although he and Zenitsu along with Inosuke, started training together, he excelled both in the matters of strength and swordsmanship. Tanjiro with his Sun Breathing is more powerful than Zenitsu.
Though he's on a journey to get over his fears and wants to be a better version of himself. However, as every Demon Slayer affiliated with a Breathing Style develops certain forms which give them an advantage in combat, Zenitsu could only learn the first form of Thunder Breathing: Thunderclap and Flash.
The user performs Thunderclap and Flash while greatly augmenting the speed of the technique. During the first display of this technique, an unconscious Zenitsu remarked that he mustn't perform this technique more than 2 times, otherwise his legs would be rendered useless due to muscle fatigue and exhaustion.
At this point Zenitsu has manifested his speed and power, and he was also able to keep up with the Demon King, Muzan, even when weakened. It's possible to say that his power easily matched the strength of a Hashira.
Among the current generation members, Shinobu and Zenitsu are the fastest characters in the series. According to the Upper Moon 2, Shinobu was the fastest opponent he had faced and was unable to react to her attacks due to its speed.
Zenitsu is clearly on the same level as Hashira. If we compare him to Shinobu, his speed is far better, while she lacks quite a lot in raw power. There is a good chance that he could beat Shinobu if the two decide to fight.
After Muzan was defeated, all the demons he created also perished immediately, so there was no point of a Demon Slayer corps anymore. As a result, Zenitsu did not get to become a Hashira even after becoming strong enough to bie one. Demon Slayer is one of the most popular anime series going on right now.
1. Gyomei Himejima. Gyomei Himejima, the Stone Hashira, is the strongest Hashira in the Demon Slayer corps in terms of strength and swordsmanship. He is the only person who uses spiked flails and an axe instead of standard swords to kill demons.
Muichiro Tokito – Mist Hashira
Though, that doesn't come in the way of his being dedicated to the Demon Slayer Corps and his teammates. In direct combat, he easily overpowered our protagonist Tanjiro so his strength is not to be taken lightly.