Psychic powers and anything beyond physical has no effect on Saitama. Which is why it is argued that even if Saitama's full name was written in the Death Note, it wouldn't even work. Saitama broke his limit so he could easily be faster than you, immune to psychic attacks and physical damage, and is without a doubt stronger. Not even his strongest punch we've seen is his... well... strongest. And another thing that comes to one's mind when pitting Saitama against someone - surviving in space. They say that Saitama can't breathe in space... yet he literally took a breath when on the moon, and wasn't affected by the temperature of space. So yes, he could survive in space. And the amount of speed along with strength it took Saitama to get from the moon back to Earth is also a great feat. Considering all the planets in the Solar System could fit between the Earth and the Moon, that's a lot of distance to take to reach Earth in a minute or less. So no, it's not just speed that matters. There are many more other reasons to back up Saitama when being pitted against these kinds of foes. I mean, Saitama also literally punched a blasted ray of energy that could destroy a star. That's like a major deflecting power move right there.