Dragon Ball Z (1989)

Five years after winning the World Martial Arts tournament, Gokuu is now living a peaceful life with his wife and son. This changes, however, with the arrival of a mysterious enemy named Raditz who presents himself as Gokuu's long-lost brother. He reveals that Gokuu is a warrior from the once powerful but now virtually extinct Saiyan race, whose homeworld was completely annihilated. When he was sent to Earth as a baby, Gokuu's sole purpose was to conquer and destroy the planet; but after suffering amnesia from a head injury, his violent and savage nature changed, and instead was raised as a kind and well-mannered boy, now fighting to protect others.