Awaken, Legendary Warrior... Son Goku, the Super Saiyan! Dragon Ball Kai: Doragon bôru kai : Season 1 Episode 47

With the help of his friends, Goku succeeds in blasting Frieza with a gargantuan Spirit Bomb! Victory seems assured, but when the monster remerges to strike a shockingly fatal blow - Goku undergoes a powerful transformation!