Through sheer will and anger, Zenitsu was able to overcome his cowardice and stay awake in battle against demons, shown during his bout with Kaigaku and Muzan, especially in the fight with the latter in which he refused to give up and persisted despite being enervated and injured.
Zenitsu Agatsuma is a part of the Demon Slayer Corps who the previous Thunder Hashira trained. Zenitsu is a skilled and able member of the organization but gets easily scared when facing demons. But as the series continues, we watch him grow as he eventually overcomes his fear of demons and fights them head-on.
While unconscious, Zenitsu is a force to be reckoned with, but his actual power is discovered when he is awake.
All of his special moves is based on the thunderclap and flash technique which operates as extensions of the thunder breathing first form technique. It is also speculated that Zenitsu is one of the most powerful demon slayers in the series.
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. Like I said, Zenitsu is usually a coward and runs away, but he stands his ground and is super angry and Kaigaku insults their sensei.
Zenitsu mastered the first form to its full capacity but failed to learn the rest. However, the first form itself is extremely difficult. With his master gone, Zenitsu can no longer learn the remaining five forms. Therefore, during his fight with Kaigaku, an Upper Moon Six, he created a 7th form.
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. It's like sleepwalking, but much cooler.
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.
1. Gyomei Himejima – The Stone Hashira.
If Zenitsu fought Akaza with his plethora of Thunder Breathing techniques, the latter wouldn't have the time to regenerate his limbs.
5 Thunder Breathing First Form
Despite this, Zenitsu has completely mastered the first form and even created more powerful variants of the technique, turning it into one of his most potent attacks. With the thunder-breathing style's first form alone, Zenitsu has managed to overpower and decapitate many demons.
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, 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. In fact, he became one of the very few to even invent a new form of Thunder Breathing. However, his dream of becoming a Hashira was never realized.
Zenitsu's character development progressed throughout the story. The more he came across powerful enemies, the more he realized his need to become strong and protect the ones he cared about. Zenitsu's desire to protect Nezuko especially gave him courage and made him realize the strength he'd had all along.
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. He was forced, not in a bad way, to train because his master, Jigger Okuwajima, saw potential in him.
Zenitsu's biggest weakness is his overwhelming fear and anxiety, often rendering him paralyzed and useless in battles. He is prone to panic attacks and tends to run away from danger, making him appear cowardly and weak.
Who is the most stronger between they two? Zenitsu is definitely faster but Tanjirou is more tactical and more versatile. Tanjirou could lose if he has no idea what Zenitsu can do, but if he does he can easily anticipate. Currently in the manga, Tanjirou is definitely stronger.
Fights against Zenitsu are usually settled in the first strike as be it his First Form or EoS Seventh Form, he specializes in a one strike iaijutsu. It ultimately depends on whether Rengoku can handle Zenitsu's first strike. If so then it's his win.
10 Can Beat: Zenitsu
Given his cowardice, it's likely that Nezuko would make easy work of him. Zenitsu also isn't the type to attack anyone he considers a beautiful girl, and we already know that Nezuko fits that description. He's more likely to try to woo Nezuko than defend himself against her.
(To himself) "I hate myself more than anyone. I always think I have to get my act together, but I end up cowering, running away, sniveling. I want to change. I want to be a competent person."
Superhuman Hearing: Zenitsu has always had enhanced hearing, being able to hear what others can't. He is able to hear a faint difference that is normally indetectable to humans in the sound of a moving human and a moving demon. His hearing gives him extra awareness for danger.
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.