DB Episode 121
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
Goku blasts King Piccolo in the back with a Kamehameha Wave. Goku continues to devastate King Piccolo, with many powerful blows. News of the fight reaches everywhere. King Piccolo disables Goku's right leg with an energy blast, but Goku merely uses the Power Pole as a crutch. King Piccolo fire deadly beams, until Goku loses his Power Pole and hits him, destroying the entire kingdom, King Furry evading death. Tien was able to save Goku from certain death, but gets exhausted. Goku prevents King Piccolo from conjuring another explosive wave, but King Piccolo manages to hit Goku and create a huge crater. Goku gets out with his Nimbus Cloud.