Huh? He's not in a habit of killing random humans. He only one punch kills monsters. If his touch was an obligatory disaster, he wouldn't be able to live a normal life at all. In reality he can even play video games without destroying the controller, most of the time. It's no problem for him to knock someone out if he can judge the correct amount of force needed. Of course that's the difficult part, but looking at his expression, I don't think he really cares. Perhaps he simply judged that the dude must be able to stand a bit more force than what he himself used against Saitama and went with that.