Quatre Raberba Winner is one of the five Gundam pilots at the center of Mobile Suit Gundam Wing: Endless Waltz, a story set in the After Colony timeline. He serves as the pilot of the Gundam Sandrock and later the Sandrock Custom, and he is the youngest child and only son of the Winner family, one of the wealthiest households in the L4 colony cluster. Born on the Winner Resource Colony, Quatre was the only one of his family's children to be born through natural birth; his older sisters were all conceived through artificial reproduction. His mother died during his birth, and his father concealed this truth by telling Quatre that he too had been conceived in a test tube. This deception left Quatre with persistent feelings of inadequacy and a sense that he could be easily replaced, despite the material comfort and privilege of his upbringing.

In personality, Quatre is gentle, mild-mannered, humble, and deeply empathetic. He is a firm believer in the ideals of pacifism and a reluctant soldier, and he openly expresses sorrow whenever circumstances force him to take a life. Among the Gundam pilots he is the most openly compassionate and the most troubled by the moral weight of war, often questioning whether violence can ever truly bring peace. He has outstanding artistic gifts, particularly in painting and music, and is a skilled violinist. He also possesses a form of extrasensory perception he refers to as the heart of outer space, which allows him to sense the emotions and inner states of the people around him. In combat he shows a genius-level aptitude for handling mobile suits, and although he lacks the raw ferocity of some of his fellow pilots, he compensates with careful strategy, patience, and the strength of the bonds he forms with those who follow him.

Quatre's motivations are rooted in a desire to end conflict and protect innocent people. Despite his privileged background, he develops a strong sense of responsibility toward others and repeatedly risks his own safety for the sake of his comrades and civilians. His early hesitation about fighting gives way to a conviction that he must do whatever is necessary to stop the wars ravaging Earth and the space colonies. That conviction is severely tested when personal tragedy strikes. After the death of his father, Quatre is consumed by grief and rage, and he uses the resources of the Winner estate, along with blueprints left by his mentor, to construct the Wing Zero, a powerful mobile suit equipped with the Zero System, a neural interface that floods the pilot's mind with tactical data. Unprepared for the psychological strain, Quatre loses his mental stability and goes on a destructive rampage through space, attacking military targets and even civilian settlements. Only the intervention of his close friend Trowa Barton brings him back to his senses, an experience that leaves him to confront the guilt of the destruction he caused.

His role in the story evolves considerably as a result of this ordeal. Having faced the most destructive expression of his own pain, Quatre returns to the conflict as a steadier and more mature figure, eventually becoming a coordinating leader among the five Gundam pilots. He also comes to embody the belief that the Gundams themselves can become unnecessary. In Endless Waltz, set in the peaceful era following the war, Quatre proposes and carries out the disposal of the Gundams by sending them into the sun, holding that such weapons have no place in a world committed to peace. When a new rebellion led by the Barton Foundation threatens the Earth Sphere Unified Nation and takes Vice Foreign Minister Relena Darlian hostage, Quatre and the Maganac Corps recover the Gundams from their course toward the sun, allowing the pilots to intervene one final time. In this final conflict, Quatre fights to end the rebellion without killing anyone, remaining true to his pacifist convictions even while piloting a weapon of war.

Quatre's key relationships reflect his role as a bridge between different worlds. He is the leader of the Maganac Corps, a group of Middle Eastern soldiers whose commander, Rashid Kurama, he once saved from betrayal; the loyalty of the Maganacs to Quatre is absolute, and they follow him into battle under his direction. His friendship with Trowa Barton is central to his story, as Trowa's intervention during Quatre's rampage is what finally restores his sanity. He works alongside Heero Yuy, Duo Maxwell, and Chang Wufei, and on at least one occasion he sacrifices his own Gundam to allow Duo and Wufei to escape, an act that reflects his willingness to put the mission and his allies before himself. He also shares a close bond with his sister Iria, who cares for him after he is gravely injured, and he is allied with Relena Peacecraft and Lucrezia Noin during the defense of the Sanc Kingdom.

Developmentally, Quatre moves from an insecure young man haunted by feelings of unworthiness, to a grieving and vengeful soldier who nearly destroys himself, and finally to a composed leader defined by genuine kindness and strength. His arc in Endless Waltz completes this transformation: he not only fights to preserve peace but also takes personal responsibility for ensuring that the weapons that enabled the war are destroyed, showing that he has learned to channel his empathy and intelligence toward building a better world rather than merely reacting to conflict. His notable abilities include exceptional mobile suit piloting skill, artistic and musical talent, strategic and organizational leadership, empathic sensitivity to others, and eventual mastery of the Zero System, which he learns to use without losing himself.