who fought with Raditz and killed him??

Raditz was killed through the combined efforts of both Goku and Piccolo. They had to team up because Piccolo's Special Beam Cannon was the only attack powerful enough to penetrate Raditz's defenses, and Goku had to hold Raditz in place, sacrificing his own life in the process. Neither Goku nor Piccolo could have defeated Raditz alone at that point in the series. Krillin and Gohan did not deliver the finishing blow.