>>46200432At the time of the Frieza saga, he didn't have Death Star-tier planet destroying attacks. He had to shoot Namek's core to make the planet unstable so it would eventually collapse. Saiyan Saga Vegeta could also do this with his Galick Gun.
However much earlier Roshi is shown destroying the moon with a Kamehameha, apparently with minimal or no delay. Powerlevels never made a whole lot of sense and weren't even supposed to.
