L'union fait la force

Furious at being stripped of his wish for eternal life by Dende, Krillin, Gohan, and Vegeta, Frieza unleashes his true power before proceeding to fight with them by firing energy blasts at his targets. Meanwhile, Piccolo comes across Nail, who is wounded by Frieza, but still alive. Nail tells Piccolo to fuse with him, because this transformation might give him enough power to defeat Frieza. Though he is reluctant, Piccolo agrees. He and Nail become one in Piccolo's body and with his newfound strength, Piccolo continues towards Frieza's ship. Back at the battle, Frieza shoots a blast at Krillin, Gohan, and Dende, but Vegeta deflects it, shielding the boys just in time. Confident in his new strength, Vegeta tells Frieza that he will defeat him, because he will soon become a Super Saiyan, the thing that Frieza fears most. Believing this statement to be a lie, Frieza tries to pummel Vegeta, but as the two grapple and power up, Vegeta's power level grows much higher than Frieza had anticipated, and he proves to be Frieza's equal, which causes Frieza's scouter to explode. After they stop their duel, Frieza admits that Vegeta wasn't bluffing, and the Saiyan Prince encourages him to transform and show his true power. (Source: Wikipedia)