Superman has been able to destroy planets for a long time with physical strength alone, something goku hasn't reach yet. Remember in the for tomorrow arc? When superman heard Kyle deep inside space and superman crashed into the moon. We was guaging his strength, and once he witnessed the collateral damage he caused on the moon he realized that he was a planet destroyer. His speed at which he was traveling when he damaged the moon can be accomplished at much less strength by a punch or kick without flying since he measured his strength on physical beings. Him just punching the planet will only cause a large crater, not destroy it because of his MASS. And that's what happened in his fight with the cannon ball planet (and superman heated the entire earth with heat vision, so goku will never escape), he flew at high speeds causing a large hole in the planet before finishing it off with cold breath (there's no escape for goku) to the brain. He realized he can destroy a planet at this point as well because he can cause an equal amount of damage by just punching it, but with less effect because of not being able to create a hole as big as the air pressure that surrounds him when he created the crater by flying. He can lift what he create by damaging the planet, he knows this because of the feat he did in our world is at war. He pushed war world(that's the whole point of giving it the name, the comic anyways) while being powered by the sun for an hour with the PLANETS thrusters going against him. The speed to propel himself(saitama) off the moon will cause a greater impact because of the shockwave he will produce. Speed plus impact plus strength equals shockwave, which means collateral damage. Ever watched crash dummies? The car that has greater speed causes the most damage when both cars crash. So the same can be duplicated by supes, the quicker he is combined with his enormous strength will produce a large shock wave causing a crater. It takes little effort for superman to cause a planet to be dstroyed by hitting it, the problem is his mass(he's not large enough). So him flying at enough speeds to destroy earth (which can be accomplished because of air pressure that he create by flying) can be duplicated or surpassed by his punch or kick on one of his supervillians or superheros. SO SOMEBODY he knows when fighting them can take a lot of power from superman back in the past.