The Spirit Bomb is an ancient technique used by Goku which he learned from King Kai. The Spirit Bomb is said to be one of the strongest techniques ever created. The attack is used by absorbing the energy of anything living, and willing to give up energy. Goku uses this attack many times in stressful situations sort of as a last hope. At first Goku`s spirit bomb is about the size of a basketball. Then it becomes the size of a small planet.
Spirit BombThe first Spirit Bomb Goku used was against Vegeta. This Spirit Bomb was created by most of the Earths energy. This attack was thrown by Krillin due to Goku being weakend from Vegeta. This attack was not enough to stop Vegeta, most likely due to being at half power.
Large Spirit Bomb
The large spirit bomb is a Spirit Bomb formed from the energy of the whole universe (besides the people). The only time it was used, was against Frieza after Goku ran out of living options. When it was thrown, Frieza suffered many injuries, but he survived it miraclulously.