Let's say he can pierce through the moon, but even so we saw Saitama making huge crater o the moon without trying as his focus. So easily both can destroy the moon if they want too. I can respect that on both.
Saitama did all that when he isn't even serious, so combine with his 100% serious state, he would really kill Saiki if he wanted too as can't see that on Saiki being above that. Ehh....Did it state he could destroy whole universe as I that might me a bit too much?