Bardock is the father of Goku and Raditz. He is a low class saiyan. His power level was of +10,000 (remember that the saiyans' power level increases after each battle), and was stronger than many elite saiyans. When he became a giant monkey, his power level increased more than ten times because he controls perfectly this transformation. Like his grandson, Gohan, he had an incredibly strong hidden inner force.
He was the leader of a group of 4 saiyans, Panpukin, Selypar, Tooma, and Toteppo, which conquered planets for Frieza. He had mixed feelings for his son Kakarot (Goku), because he felt a strong paternal love for his son, but he also felt shame because Goku was the "weakest" saiyan that has ever lived (we all know that that is a big lie! XD). One day, Bardock and his team were sent to conquer a planet called Kanassa. They easily conquered it, but a native from the planet called Tooro attacked Bardock in the back of his neck. This attack gave Bardock the ability to watch the future. Tooma attacks Tooro, and then Bardock kills Tooro, but falls unconscious. Meanwhile, Frieza is shcoked to know that only four low class saiyans easily conquered a planet with a very strong popoulation (Kanassa), so he decides to kill all the saiyans to prevent them from becoming even more powerful. So he sets Planet Vegeta as his destination to destroy it.
Back in Planet Vegeta, Bardock recovers from the attack, but starts having horrible visions: Planet Vegeta destroyed by Frieza, and Goku becoming a warrior. He goes to where Goku is remembering his visions, and leaves because his team was sent to conquer another planet while he was still recovering. When he reaches the planet, he finds a destroyed village which he thought was made by his team. He searches for them, and finds them DEAD! :O Only Tooma was still alive. Tooma tells Bardock Fieza's plan and dies. :( Bardock cleans Tooma's head and puts Tooma's bloody handerchief around his head. Immediatley, a group of mercenaries commanded by Dodoria (one of Frieza's bodyguards) appears. Bardock asks for an explanation but instead gets attacked. He defeats easily the mercenaries, but gets attacked and defeated by Dodoria himself. Believing he defeated Bardock, Dodoria returns to Frieza's ship. Bardock, remembering his visions, gets up and goes to Planet Vegeta all wounded up.
As he reaches Planet Vegeta, Goku is sent towards Earth and passes next to Bardock. When he reaches Planet Vegeta, he warns everybody about Frieza's plan, but no one believes him and they ridiculize Bardock >:(
Enraged, badly wounded and alone, he faints and has another vision. He sees Goku all grown up in Namek, and then sees Frieza destroying Planet Vegeta. He wakes up, and believing that there is still hope, he decides to kill Frieza to save the future and goes to space to do it. As he gets near the ship, millions of Frieza's soldiers attack Bardock, but fail even though Bardock is heavily wounded because of his extraordinary power ! Finally Bardock meets face-to-face with Frieza. Bardock throws his Final Spirit Cannon against Frieza's Death Ball (Death Ball = Death Star? What a coincidence in the names XP). Bardock's attack gets absorbed by Frieza's attack because he was too wounded to use all his strength in that attack. Frieza launches the Death Star, sorry Death Ball (hahahaha), towards Planet Vegeta killing his soldiers (yeah, his own soldiers. What a boss right?), Bardock and destroying Planet Vegeta. Before dying, Bardock has a vision of Goku fighting against Frieza avenging his death and the death of the most awesome and strongest warrior race of all: the saiyans! Seeing that, Bardock dies happy. While Goku goes towards Earth, Bardock's voice is heard saying
"Kakarot, you must fulfill my objective. You will be the one that avenges the death of the Saiyans and the destruction of Planet Vegeta."