Monev the Gale is the first member of the Gung-Ho-Guns to fight Vash. Millions Knives locked him in a cell to train his body for twenty years in order to gain the necessary skill and power to face Vash.
He wears a powered battle suit and carries two high-powered chain guns on his arms. These guns fire extremely fast due to the pressure chambers located on his back and have tremendous stopping power, enough to tear through entire buildings. He also carries a wide variety of weapons in a big cloth rucksack, including an enormous minigun, powerful enough to punch through a bank vault.
Monev was sent by Legato to attack Vash, leading to a destructive brawl throughout a city, leaving many dead and shooting off Vash's cybernetic arm. He is eventually defeated by Vash, who nearly breaks his oath to never kill out of rage for all the deaths caused by Monev. Vash regains himself and spares Monev, and Monev surrenders his coin and leaves. His murdered and crucified body is later displayed by the next Gung-ho Gun, E.G. Mine, when Mine challenges Vash.
His life is spared in the anime, but is then killed by E.G. Mine along with Dominique the Cyclops due to his failure.
In Trigun Stampede
Monev was a boy named Rollo, who lived with his mother in the Windmill Village. Due to the precarious conditions in which they lived, Rollo's mother was a strictly religious woman, where she prayed every day for God to save them. The city dwellers used to use their children as "sacrifices" to the God they worshiped, as they believed this would later result in blessings. In fact, the town was controlled by Knives' cult, the Eye of Michael, and used as one of their testing centers so that William Conrad could do his experiments on children.
Vash was already known by Rollo's family and both ended up meeting after the boy tried to run away from home. Rollo explains to Vash that he is sick and will likely die before he grows up. Vash then promises that he will get the medicine he needs, but when he returns it is too late.
One night, Rollo was sent as one of these sacrifices, he was taken by William and used as a test subject, resulting in the accelerated growth of his metabolism, which deformed his body and turned him into a muscular monster. William, instead of discarding him, puts an implant in his brain to heighten his emotions and leading to accelerated development of athletic abilities. Then he equipped Rollo with heavy weapons and trained him for years as a killing machine, transforming him into Monev the Gale.
Monev's appearance is reminiscent of Venom (even more so in the manga), from the Spider-Man series, especially in contrast to Vash's red coat. Yasuhiro Nightow is known to be a fan of Spider-Man and McFarlane related products.