XXXG-00W0 Gundam Wing Zero

When the Tallgeese prototype (the first mobile suit of the After Colony timeline) was completed, the five scientists who had supervised its design and construction rebelled and went into hiding. They collaborated to produce a new mobile suit, one which could outperform the Tallgeese, and which would be constructed from Gundanium alloy. This "Gundam," the Wing Zero, was developed to the blueprint stage but never constructed, as it was considered too powerful for any pilot. Each scientist took a copy of the plans and used it to develop their own Gundams: the ones seen at the beginning of Gundam Wing.

The existence of Wing Zero is first revealed in episode 21, when Quatre Winner discovers a copy of the blueprints and begins work on the Gundam to replace his then-destroyed Gundam Sandrock. In the same episode, Quatre's father is killed by OZ. The completed Wing Zero first appears in episode 24, with Quatre at the controls, driven mentally unstable from the combination of his father's death and exposure to the ZERO System. Heero Yuy and Trowa Barton (both working for OZ, the former unwillingly) are sent to take on Quatre and Wing Zero. The pair are able to return Quatre to normalcy, although Trowa nearly loses his life in the process, and Heero and Quatre are captured. OZ soldier Trant Clark forces Heero to test the ZERO System, but he and Quatre escape and return to Earth in episode 26.

Trant retains Wing Zero, testing it again with Duo Maxwell at the controls in episode 32. After Duo escapes, Trant attempts to fight Duo's Gundam Deathscythe Hell with Wing Zero, dying in the process. Trant's body was never shown to be recovered after his death, however, when OZ plans to destroy the Gundam in episode 34, his body is never shown or hinted to have been removed from the cockpit, though the suit is empty when Zechs Merquise sacrifices his Tallgeese in order to claim Wing Zero for himself (This may be a reference to the EXAM System from the Universal Century, which saw the test subject for that system be absorbed by the machine. However, there is nothing to substantiate this theory. Presumably, OZ removed his body for the sake of Trant's family, and this would be why there is no corpse in the suit when they attempt to destroy the suit.).

Zechs confronts Chang Wufei in episode 35; he at first attempts to become the Gundam pilot's ally, but the effects of the ZERO System forces him into conflict. He then uses Wing Zero to return to Earth in an attempt to prevent the dissolution of the Sanc Kingdom in episode 37, and fights Heero, who is piloting the Gundam Epyon. After their duel ends in a draw, they exchange Gundams before parting ways, leaving Heero with Wing Zero (becoming a perfect match for Heero due to it being essentially an upgraded Wing Gundam).

Heero and Wing Zero return to space in episode 41, and over the next two episodes Wufei and Trowa both pilot Wing Zero, allowing them to work through their personal problems (Wufei discovers his true enemy and joins the Gundam team, while Trowa regains his memories that he had lost after his near-death experience). During the final episodes of the series, Heero is shown at least twice speaking to Wing Zero as though it were alive and holding a conversation with him. The first is shown when Heero is preparing for the final battle against the White Fang, preparing a copy of the ZERO System for installation into Quatre's rebuilt Sandrock, and again in the very final episode of the series, as he asks the suit to help him, and the suit responds to the plea almost immediately. Heero uses the Gundam in another duel against Epyon, defeating Zechs, before using Wing Zero's twin buster rifle to destroy the wreckage of the battleship Libra superweapon before it can impact with Earth.

Following the events of the series, four of the Gundams, including Wing Zero, are collected and sent towards the sun for disposal. When the Barton Foundation, led by Mariemaia Khushrenada, begins to perform the original Operation Meteor, Quatre sets out to retrieve the four Gundams, sending Wing Zero to rendezvous in space with Heero, following his efforts to prevent the de-orbiting of Colony L3 X-18999.

After retrieving Wing Zero, Heero flies to Earth to save the kidnapped Relena Darlian, but is intercepted by Wufei in the Altron Gundam (who is on the side of the Mariemaia Army), and the two Gundams duel each other above Earth's orbit. During the battle, Heero doesn't fight to his fullest extent (due to him believing the duel to be pointless) and Wing Zero receives heavy damage from both Altron and the re-entry into Earth's atmosphere. Eventually, Heero gives up the fight and causes Wing Zero to sink into the ocean, at which point Wufei comes to his senses. Sometime later, however, Wing Zero re-activates on its own and supposedly convinces Heero to complete his mission, yet again implying the Gundam has a mind of its own.

Wing Zero arrives in the sky at Brussels, where the other Gundams are fighting, and Heero aims its twin buster rifle at the shield-protected Presidential Building where Mariemaia and her troops are hiding in. Heero fires the rifle three times with precise accuracy and succeeds in destroying the bunker shields. However, due to its already badly-damaged state, the continuous recoil of the rifle (along with enemy fire from the compound below) proves to be too much for Wing Zero to withstand; causing the Gundam to start falling apart while firing the second shot and then explode altogether while firing the third shot, though the remains of its torso crash to the ground which allows Heero to survive and climb out of the wreckage (although barely able to stand). After Mariemaia's surrender, the rest of the Gundams are also destroyed, along with all other mobile suits.