Dragon Ball Z - episode 84 - 02 Apr, 1991

Now in his final form, Frieza seems unstoppable. With a single energy beam, he immediately kills Dende, since he is the reason the tyrant's enemies came back from near-death, via the young Namekian's healing powers. Angry at Frieza's murderous act, Piccolo, Gohan, and Krillin throw everything they've got at him, but Frieza easily dodges them. When Frieza fires the same blast at Gohan, Vegeta steps in and knocks him down, just in time for the beam to miss his victim. Vegeta tells Frieza that he has now become a Super Saiyan. Unafraid, Frieza takes him on. (Source: Wikipedia)