Goku specifically said that he was holding back, or he might kill him, translation team didn't really do a good job on that one.
He's been tuning his SSB down tremendously. Right now he only uses it to impart terror when he's testing the team members to test their resolve. It's also training to him more than likely as well so he doesn't nuke weaker fighters to a crisp. It clearly doesn't phase 17/18 since they can't sense ki. Really throws the guys that can sense ki for a loop though. the gods, Krillin, etc. Krillin felt as though he had been hit by a lightning bolt.
The show writers have also been super hard on playing up what happens when you get lax and don't pay attention to your surroundings. Goku getting merked by the laser gun, the bullet wounds on goku and krillin, 18 kicking away the kamehameha, goku getting dropped through the floor with the kienzan.
It's all a part of the setup to a) scare the shit out of every non near god ki tier fighter, the gods themselves, and b) to be used as a plot device to worf effect characters.
XI Wiki



