The Demon in the Snow

is episode 19 of the original Naruto anime.

Synopsis
Gatō, with his men, plans to kill Zabuza. He told Kakashi that their fight is over to which he agreed. Naruto got angry when Gatō stepped in to Haku's dead body. Zabuza said that he only uses Haku. Naruto, finally convince Zabuza saying that Haku loved him and so help him fulfill his dreams. Finally, Zabuza appreciate Haku's sacrifice and broke his heart in fighting them, and happy to fight them as his final opponents, and borrow Naruto's kunai to prepare to take his revenge on Gatō, wielding a kunai on his mouth since his arms were broken by Kakashi, but before he could get near to Gatō, he was stabbed multiple times by his men, but he successfully killed the latter in his injuries.

Sasuke was alive, which Sakura and Naruto became happy. The men were scared away thanks to the villagers, Naruto and Kakashi's (fooling them) efforts. The dying Zabuza requested Kakashi to bring him beside Haku. He said that he want to go same place as him. Kakashi said that he can go there also.

The team buried them and Zabuza's grave was with his sword, Kubikiribōchō along. Naruto, saying he want to have his own ninja way. He bade goodbye to Inari, and Tazuna named the bridge as the Great Naruto Bridge.

Trivia

 * In the manga, when attacking Gatō, Zabuza cuts his head off, rather than slashing him up and pushing him into the sea.