Zaku Abumi

was a Genin-level ninja from Otogakure. He took part in the Chunin Exams under orders from Orochimaru to kill Sasuke Uchiha.

Background
Unlike his teammates, a glance into his past and how Orochimaru recruited him was given, making him a far more dramatic character. The anime showed that he was an orphan living on the streets who hustled by stealing for a living, and was almost always beaten for it. Orochimaru had told him he had potential and liked the strength in his eyes. Zaku refused to give up, even at the cost of his own life.

Chunin Exam arc
Zaku and the rest of Team Dosu attacked Sakura during the second phase of the Chunin Exams in their attempt to kill Sasuke. When Rock Lee arrived to help her, and used Front Lotus on Dosu, Zaku emitted sound air into the ground to soften his landing. Team 10 soon came to help as well, and took control of Kin's body, prompting Zaku to attack her to get her out of the way. Sasuke woke up during the attack, and noticed that someone had harmed Sakura. Zaku took credit for this, prompting Sasuke to dislocate his arm as punishment. Team Dosu promptly fled.

In the third stage preliminaries, he was matched against Shino Aburame. Because Zaku's arm was in a sling from his encounter with Sasuke, Shino advised him to forfeit the match. Zaku refused, and instead attacked Shino with his one good arm. In attacking Shino, Shino was given an opportunity to box in Zaku with bugs, forcing Zaku to choose between attacking him or attacking the bugs, leaving the other to attack Zaku from behind. Zaku chose to attack both, and pulled his other arm out of its sling. As Zaku prepared to blast the two opposing forces, his arms detonated, making them unusable and putting him in immense pain. (In the manga, his right arm was even blown off of his body. In the anime, his arms were still severely damaged but still attached to his torso.) As Zaku writhed, Shino revealed that the tubes in Zaku's arms had been filled with his bugs, causing the pressure of Zaku's attack to go outward when it couldn't escape.

Konoha Invasion arc
Zaku, along with Kin, was later betrayed and used by Orochimaru as sacrifices to summon Hashirama Senju and Tobirama Senju from their graves with Impure World Resurrection.

Abilities
Like many Sound ninja, he had been physically altered with unnatural enhancements that enhanced his abilities; in his case, he was fitted with hollow air tubes that extended through his arms and opened through his hands, allowing him to propel a combination of air pressure and sound in various ratios, controlled by his chakra. In his fight against Choji, Zaku claimed to be able to control the sound more precisely than simply firing it in one direction, but this was never shown.

Trivia

 * Zaku's name is derived from "to cut", which relates to his "air cutter" attack. It is also the sound of a person walking on snow or sand. With the former name meaning, he and his two teammates have names relating to swords, fitting based on their aggressive behavior and deadly intentions. However, based on the latter meaning, he and his two teammates all have names that come from onomatopoeias, fitting since they come from the Hidden Sound Village. Their naming pattern (Slash, Clang, and Crunch) is similar to that of Snap, Crackle and Pop.
 * The kanji on Zaku's shirt is 死 ("Shi", death).
 * During a flashback in the anime Zaku defeats a ninja from Takigakure. Based on his outfit the defeated nin was most likely a chunin.
 * Abumi means stirrup. It's also the Japanese name for one of the three ear bones, stirrup.