Nicholas D. Wolfwood (ニコラス・D・ウルフウッド, Nikorasu Dī Urufūddo), also known as Nicolas the Punisher, is a member of the Eye of Michael, an organization of assassins founded by a plant worshiper. After showing potential in the orphanage in which he is raised, Chapel trains and modifies him, giving him enhanced abilities and the ability to regenerate from heavy injuries using special vials, though he ages much faster than normal. He is given a special large cross-shaped gun called the Punisher, which contains two machine guns and a rocket launcher. Wolfwood later shoots Chapel and takes his place in the Gung-Ho-Guns in an attempt to kill Knives. He fails to do so, and is instead sent by Knives to protect Vash until he is able to meet him. After Vash is captured, Wolfwood rescues him, and battles his childhood friend, Livio, and his master, now in a wheelchair. He manages to kill Chapel and defeat Livio, but having overdosed on the regenerative vials, he soon dies while talking to Vash.
In the anime, Wolfwood is raised by an abusive guardian, who he later shoots and kills. He is taken in by Chapel, who trains him to be his successor. He meets Vash while he is stranded in the desert, and the two join forces. Wolfwood's purpose is to raise money for the children in the orphanage he runs, trying to keep other children from suffering as he did in his own childhood. He initially holds the ideals that he must kill, though he eventually comes to accept Vash's ideals. He eventually fights his master, but spares him after defeating him. Legato controls Chapel and forces him to shoot Wolfwood, who stumbles into a church. He spends his last moments reflecting on his life and making a final confession before dying. Vash then takes his gun as an act of honor, and uses it fighting against Knives. During the course of the series, Wolfwood develops a relationship with Milly that crosses from close friendship into romance, sleeping with her shortly before his death.