Mobile Fighter G Gundam

Rather than having a war between the colonies and the Earth, a fighting tournament is held. Called the Gundam Fight, it is held once every four years by the United Colonies Federation. Each country would send its own representative, that would pilot a Gundam, and the Gundams would then fight on the Earth until only one is left, and that Gundam's nation will then be able to obtain sovereign rights over all the nations, until another nation wins in the next Gundam Fight. This series is set in Future Century (FC) 60, during the 13th Gundam Fight and it focuses on the Neo Japan Gundam Fighter Domon Kasshu, who is in the fight as much to win as well as fulfill his own mission of tracking down his brother who had stolen a mysterious Gundam; the Devil Gundam from the Neo-Japan government.
(Source: Wikipedia)

In the Year FC 60, much of mankind inhabits space colonies which orbit the Earth. Dominance over the colonies is decided once every four years by a large tournament in which each nation sends a single representative to fight the others with a giant robot called a Gundam. Domon Kashuu is selected to represent Neo-Japan in one of these tournaments, but he fights less to ensure his nation's victory than to find his brother, who has been blamed for the deaths of Domon's parents and the disappearance of a very dangerous weapon, the Dark Gundam or Devil Gundam.

(Source: Anime News Network)

Neo Belgium's Gundam Fighter John Browning is shunned in his hometown after dropping out of the 13th Gundam Fight. Determined to participate in the Gundam Fight, even if unofficially, John attempts to assassinate Rain, only to be confronted by Domon and Rain after it is revealed his target is a hologram.