"Sharingan no Kakashi" (写輪眼のカカシ). Original Air Date: November 28, 2002.

Kakashi reveals the full power of his Sharingan, copying Zabuza's water-based techniques—most notably the Water Dragon Bullet Jutsu —to overwhelm and defeat him.

This episode is a pivotal moment in the Land of Waves Arc , establishing the power levels of jonin level ninja. Kakashi: Sharingan Warrior! | Narutopedia | Fandom

Before Kakashi can deliver a final blow, a mysterious "hunter-nin" (later revealed as Haku) appears, seemingly killing Zabuza with senbon needles and taking the body away.

Naruto and Sasuke execute a brilliant strategy involving a Fūma Shuriken and Transformation Jutsu to trick Zabuza, successfully freeing Kakashi from the Water Prison Technique.