Broly

Broly, also known as the Legendary Super Saiyan, only appears in certain movies and apparently has nothing to do with the real timeline. His incredible power was controlled with a device by his father, Paragus, who hated King Vegeta for trying to kill the only Saiyan on-planet that was stronger than Prince Vegeta: the infant Broly. When Vejiitasei was destroyed, the infant Broly summoned his power to save himself and his father, but as Broly matured he became increasingly difficult to control, hence the devices. Paragus had planned revenge on Vegeta, but Goku got mixed up in the whole business and the Z Senshi ended up fighting Broly, the most powerful Saiyan ever with a mean streak a mile wide. He particularly hates Goku because they were in the same infant unit together, and Goku, although he had a much lower power level, made Broly cry. Broly therefore goes insane with rage each time he sees Goku.

In the first movie in which he appears he is defeated by the Z Team. He has a mean streak several galaxies wide and unimaginable power. In the second movie he is on Earth, still trying to get revenge on Goku, but instead encounters Trunks, Goten, Videl, and Gohan. Gohan and Goten execute a perfect Kamehameha to defeat him with the help of their dead father. In the third movie Broly is merely a clone turned bio-warrior and although he still posseses incredible power his mental capacity is apparently nil. His vocabulary is reduced to a series of screams and the word "Kakarotto". This apparent idiocy has made him the brunt of numerous jokes on assorted humor pages, but keep in mind he did at one point in time possess intelligence, as seen in the first movie in which he appears.