Momochi, Zabuza was born in Kirigakure. During one of Kirigakure's annual events of pitting graduating ninja against each other, Zabuza singlehandedly killed all of his peers, bringing an end to the ritual and causing him to be called the "Demon of the Hidden Mist". Zabuza would go on to become one of the Seven Shinobi Swordsmen of the Mist where he acquired his zanbatō, and also became a member of the Kirigakure ANBU. At some point in time, Zabuza found a young boy named Haku wandering the countryside, and offered to take Haku in as his tool. Haku accepted and became loyal to Zabuza, learning from Zabuza and protecting him whenever necessary. Zabuza eventually attempted a coup d'état on the Land of Water by trying to assassinate the Mizukage. The coup failed, forcing Zabuza and his subordinates to leave the country. In the hopes of gaining funds for a second coup, Zabuza became a hired assassin, killing anyone if the price was right.
Being from Kirigakure, Zabuza excels in water-oriented jutsu, some of which are exclusive to him. With Water Release: Water Dragon Blast Technique (Suiton: Suiryūdan no Jutsu, Viz "Water Release: Water Dragon Missile") he can form a dragon from the surrounding water to attack others as needed. His Water Release: Great Waterfall Technique (Suiton: Daibakufu no Jutsu, English TV "Water Style: Giant Vortex Jutsu") allows him to fire a massive spiraling blast of water at an opponent. In addition to the offensive capabilities of his water jutsu, Zabuza is very skilled in assassinations. By blanketing the area in mist with Hiding Mist Technique (Kirigakure no Jutsu, Viz "Art of Hiding in the Mist"), Zabuza can blind an opponent and use his training as an ANBU to find them based on the sounds they make. Once found, Zabuza uses Silent Homicide Technique (Muon Satsujin Jutsu, English TV "Silent Killing Jutsu") to kill the opponent without their noticing his presence. This talent with assassinations is very well-known, as even the ninja of Konohagakure are familiar with Zabuza's history.
Zabuza is hired by Gato to kill the bridge builder Tazuna. After his initial attempt fails to kill Tazuna and his escorts (Kakashi Hatake and his students) and leads to his defeat, Zabuza and Haku seek a rematch after he recovers. Once tracking down Team 7 again, Zabuza is drawn into battle with Kakashi while Haku deals with his students. Although he tries to avoid Kakashi, he is eventually restrained and Kakashi prepares to kill him with his Lightning Blade. Before he can land a blow, however, Haku appears to use himself as a human shield for Zabuza, fulfilling his promise of being a tool for his master. Zabuza is freed as a result of Haku's intervention and tries to attack Kakashi, though Kakashi is able to avoid the attack and make both of Zabuza's arms useless. With Zabuza no longer able to fight, Gato arrives with his henchmen to finish the job instead, ending the battle between Zabuza and Kakashi. Naruto Uzumaki, however, is angered that Zabuza has yet to show remorse for Haku's death and explains Haku's devotion to him. Brought to tears by his words, Zabuza reveals that he did care for Haku and decides to repent for what he has done. After taking a kunai in his mouth, Zabuza charges through Gato's men, being stabbed multiple times along the way though eventually reaching and killing Gato. After collapsing due to his injuries Zabuza asks to be brought to Haku's side, wanting to be by his side in death as Haku was by his in life. Kakashi complies, and in his dying moments Zabuza wishes to go to the same afterlife as Haku.
Shinobi World War Arc
In preparation for the Fourth Shinobi World War, Zabuza is resurrected by Kabuto Yakushi to fight against the Allied Shinobi Forces, before being mobilised alongside Haku, Gari, Pakura and Toroi. Overhearing Zabuza as he told Haku that they were no longer in the afterlife, Gari informs them of their current situation, infuriating Zabuza because he didn't want to obey someone who would stoop so low as to use the dead. Ambushed by the Surprise Attack Division, Haku protects them both from the explosive tags carried by Sai's ink birds, but Zabuza calls it unnecessary once he observes the others regenerating. This irritates Zabuza further, who remarks that not only were they brought back, they were also made impossible to kill. Stating that he was the only one amongst his group to not possess a Kekkai Genkai, Zabuza storms the recently grounded opposition but is intercepted by Kakashi, whom he didn't expect to fight again. Greeting Sakura and noting her growth since they last met, Zabuza enquires about Naruto, learning from Kakashi how famous he had become since his death.
As Kabuto erases their consciousness, Zabuza pleads with Kakashi to stop him no matter what it took, as his humanity was already dead. Enveloping the battlefield in a thick mist, Zabuza then assualts the Third Division, until he is confronted by Kakashi. Amidst the battle, the previous generation of the Seven Ninja Swordsmen of the Mist are summoned to the field in order for Akatsuki to retain the upper hand, with Zabuza soon joining them whilst wielding his broken Kubikiribōchō.
In the end of the fight Zabuza is captured by Ensui Nara and sealed by Maki.
In a world full of ninjas from rivaling villages who more or less have superpowers, how can you not expect there to be epic clashes as these shinobi fight for life and honor? Is your favorite in this list? (Spoilers for Naruto and Naruto: Shippuuden)