Cyandog

Spyke has, at first, Cyandog, a Medarot who always loses because Spyke has a medal that's incompatible with his body (a Monkey medal, made for hand-to-hand combat, in a Canine body, made for shooting). He later upgrades to the more modern Krosserdog body, but he keeps the medal. This happens after Cyandog runs away from Spyke after feeling tired of being useless. He joins the Rockers and robattles Metabee, who notes that the robattle will not be like any other robattles he's had with Cyandog. Metabee finally got the upper hand but in return would destroy each of Cyandog's parts one after another. Yet Cyandog doesn't give up and continues to attack Metabee. He misses but Metabee blasts him in the head with his laser cannon. Believing the robattle to be over (as his head part was now at 100% damaged), Metabee was shocked to see Cyandog get back up again (with this being the only time a Medarot has survived from a function cease). Metabee, having no other choice, decided to destroy Cyandog, but, before he could, Spyke interfered. After a small conversation with his old medarot, Cyandog finally goes down and his body is never used again (probably due to all of the damage that the body took from being blasted by Metabee).

(Source: Wikipedia)