Broly was the Legendary Super Saiyan born in more than a thousand years. At birth, he had an unusually high level of strength for a Saiyan. Broly's exceptional gifts marked him as being the Legendary Super Saiyan. King Vegeta feared this and ordered for his execution. His father, Paragus, begged to spare his life. King Vegeta ended the argument by blasting him. As Broly's execution was carried out both he and his father were left to die. While Paragus barely survived the blast, Broly survived the attempted execution only to grow stronger. On that same day, Frieza acted on his own fear of the Super Saiyan legend and attacks Planet Vegeta. Amid the destruction, Broly encased himself and his father in a powerful shield of energy and escaped.

As great as Broly's power was, his emotional instability was greater. Fearing Broly's state of mind, Paragus had a scientist create a special control device to keep Broly controlled. Successful in controlling him, Paragus planned to have revenge on King Vegeta's son. When Broly encountered Son Goku, Broly became erratic though he was brought back under control by Paragus. Eventually, Broly overpowered the control device, and fully manifested his powers. No longer under the device's control, he unleashed his fury on Goku, Vegeta, Son Gohan, Future Trunks, and Piccolo, and defeated them all. The Z warriors eventually channeled their energy into Goku, who used the energy for one last powerful blow that seemingly killed Broly.

Broly survived and entered a Saiyan Space Pod, coincidentally landing on Earth. The crater caused by his landing filled up with water and froze over time, during which he fell into a deep sleep. During this time, Gohan grew up, Son Goten was born and Goku was in the Afterlife. In an adventure to collect the Dragon Balls, Goten, Trunks, and Gohan find themselves in the mountain range where Broly crashed. Broly awakens and Goten, Trunks, Videl, and Gohan became victims to his rampage. It was only after some spiritual help from Goku that they were able to send Broly straight into the sun.

(Source: Wikipedia)