Freezer is one of the most powerful bad guys in DBZ. According to the story, he ruled the Universe and
conquered many planets incluiding planet Vejita. He feared the Saiya-Jins so he
destroyed the planet, and he thought that only two were left (Nappa and Vegeta). He then heard about
the Namek Dragon Balls and went there to wish for the eternal life. He then got killed by SSJ Gokou. His
father and him appeared again and went to conquer Earth but got defeated by SSJ Trunks (from the future).