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.
So in a nutshell, Zenitsu wasn't able to master the other five forms, but later in the Infinity Castle Arc, during the battle with Kaigaku, Upper-Rank Six Demon, he created a Seventh Form: Flaming Thunder God.
1/7 Seventh Form: Honoikazuchi No Kami
This mastery allowed Zenitsu to form a Seventh Form of Thunder Breathing that is unique only to him: Honoikazuchi no Kami. While this move might seem similar to Thunder Breathing's First Form, the speed and power of this technique are on a whole new level.
Thunder Breathing has 6 standard forms in total, with the first form said to be the foundation for all the other forms. However, Zenitsu Agatsuma developed a Seventh Form in order to stand on equal ground with Kaigaku, his former senior disciple under Jigoro who had become the Upper Rank Six of the Twelve Kizuki.
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.
Given how talented Tanjiro is, it's likely he'd defeat Zenitsu, even if the latter could fall asleep and call on his powers. Tanjiro's demonstrated his ability to take down more powerful demons and adapt to training on more than one occasion, so it just makes sense.
Why Zenitsu could not become a Hashira in Demon Slayer. Fans have wondered whether Zenitsu ever got to realize his dream of becoming a Hashira at all. Unfortunately, the answer to this question would be, no, he did not. Zenitsu, along with Tanjiro and Inosuke got way stronger than average corps members with training.
When facing Kaigaku during the Infinity Castle arc, Zenitsu debuts his brand new exclusive Seventh Form to Thunder Breathing. With this, Zenitsu finally has more than one tool in his arsenal and has overcome his own personal doubts and fears.
His most useful technique is Honoikazuchi no Kami — a technique created by Zenitsu himself that is incredibly powerful and requires so much speed that Zenitsu's haori is completely ripped to shreds during its execution.
Zenitsu speed is nearly that of light. To downgrade it, it is still invisible to naked eye, i.e. more than 51 Mach. Zenitsu speed with his sword skills just blitz Kaminari.
Zenitsu creates his own form called Seventh Form: Honoikazuchi Nokami. Through this form, he is able to conjure a creature akin to a dragon that breathes thunder and fire. When combined with God Speed, his power and strength increase, giving him the ability to defeat demons like Kaiju, from the Upper Moon Six.
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.
History. Jigoro was the instructor of Zenitsu and Kaigaku as the former Thunder Hashira. Kaigaku managed to master all of the Thunder Breathing Forms except for the first Form, meanwhile Zenitsu had only managed to master the first Form and none of the others due to his inexperience.
Tanjiro isn't Faster Than Zenitsu, not at all. He is Strong but Slow. So, Zenitsu Will Probably Chop Him Down to bits before tanjiro even pulls out his sword properly.
To sum it up, it is possible for Zenitsu to fight without fainting and it has been shown clearly in the manga. While he only perfected the first form, he trained hard enough to create a new form that didn't exist before.
Zenitsu always performs a single form because that is the only form he knows. His attack always start with this positioning, and end result is this way.
13/15 Zenitsu Agatsuma Defeated An Upper Moon On His Own
He falls asleep when he crumbles under the weight of his own fear, and his body fights on instinct alone, utilizing his Thunder Breathing Style. He proved that he can be a capable fighter even while awake, defeating Upper Moon 6 on his own.
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.
1/10 Tenth Form: Constant Flux/The Dragon of Change
The most powerful water move in Tanjiro's current skill set, this is a form that gets more and more powerful with each rotation that he puts in. It's number one on the list because it has, theoretically, no ceiling when it comes to its intensity.
3/10 Did Not: Inosuke Hashibira Trained With Tanjiro But Never Got His Mark. Inosuke, like Zenitsu, spent most of the series traveling with Tanjiro.
Having a split personality entails the presence of another person inside your mind. However, in Zenitsu's case, fans have witnessed him utilizing his skills and training, something akin to his sleeping form, and having more of an assertive personality when he is particularly worked up.
Despite her petite appearance, Mitsuri Kanroji has a special muscular composition that makes her muscles eight times denser than an ordinary human's. She is also more flexible than the other Hashira. These two strengths balance out her being the slowest runner out of all the Hashira.
We hear the Elder Brother Spider Demon say that Zenitsu could barely move his limbs, but he was still defeated. Judging from this, we can say that on a scale of 1–10, Zenitsu's strength is at an impressive 8.5/10.
Zenitsu is an incredibly powerful Demon Slayer, but he's always in fear. His nerves calm down when he's asleep, so that's when he awakens his “powers”. MANGA SPOILER AHEAD!!! Zenitsu becomes a lot more courageous and stands up to a powerful demon while wide awake.