Fires an energy blast that would've destroyed Namek had the Dragon Balls not been used to protect it

Gathering his remaining strength, Goku dashed forward through the hail of energy attacks. Though he knew Vegeta could sense his energy, he hoped the clouds of dust would obscure him for at least a moment. Holding both hands at his side, he started to charge his attack. "KA-ME-HA-ME..."

As the dust cleared, he saw Vegeta hovering above him, the golden light of his transformation overpowering the glare of the Namekian suns. To Goku's horror, the Super Saiyan was charging his own attack. "Now you will pay!" roared Vegeta. "Super Galic Flash!"

"-HAH!" screamed Goku, releasing the bright blue energy wave. It met Vegeta's golden beam a dozen yards above him, producing a shockwave that made the whole planet seem to shudder.

Goku's beam, strengthened by the 25x kaioken, began to push back Vegeta's attack. The Super Saiyan had been too confident in his strength, and he had held back just a little too much. Unlike the Kamehameha wave, Vegeta's attack couldn't be amplified after it had been released, and Vegeta could do nothing to overcome Goku's beam. He felt himself losing control of his attack.

Suddenly, Goku felt his strength ebb. The 25x kaioken was too much; he couldn't sustain it any longer. Both Saiyans felt their energy beams fail simultaneously, and they watched as the golden and blue fire coalesced into a crackling ball of destructive energy between them.

As Goku's kaioken continued to drain, he summoned the last of his remaining strength and blasted off, flying as low and as fast as he could. Vegeta followed in a golden streak. This was the end, Goku was sure; that ball of energy now sinking slowly behind them made Frieza's Supernova attack seem like a mere firecracker. Namek was going to blow up, and there was nothing he could do to stop it.

Moments earlier…

...

"Porunga," Piccolo began, "Is it within your power to make our home safe from being destroyed? Can you form some kind of protective shield or barrier around planet Namek?"

"Hmmm," the dragon growled, his voice deeper than thunder. "I do not know, but I will try." Porunga's red eyes began to glow brightly as he seemed to be exerting a lot of effort. Piccolo waited patiently, hoping his idea would work.

He had been the one to suggest to King Kai that the final wish be used to protect Namek. The planet had already sustained heavy damage from the battle between Vegeta and Frieza, and who knew what Vegeta would do once Frieza was out of the way. He might leave under a false pretense of peace and blow up the planet from space. Or, if he decided to battle Goku, who could know the kind of destruction their fight might cause? Overall, it seemed like the only other option would be to abandon the planet entirely and evacuate everyone. Piccolo wasn't about to make the Nameks sacrifice their home, and King Kai agreed this would be the best way.

"Your wish has been granted." Porunga reported with pride. "Now, farewell." The dragon began to glow white and then all of his body shot like lightning back into the dragonballs. The balls, which glowed and hovered in the air, suddenly launched themselves across the planet, each going to its own far corner. The dark sky slowly faded back to a calm green.

...

The blast caught the two Saiyans only a few seconds later, sending both of them tumbling out of control. As he spun through the air, completely out of energy, Goku wondered what had happened. Was the planet exploding already? It couldn't be - the ball of energy hadn't had time to sink to the core. What had caused the blast to detonate on the surface?

- Bringer of Death Chapter 12