If he could prove that he was indeed a supernatural being, able to do something which contradicts the laws of nature, then I would have to believe, wouldn't I? All he would have to do is, say, give new legs to an amputee, in a flash, immediately, with no external assistance, under proper supervision (to avoid fakery). Or make gravity reverse itself. Something which is technologically impossible, but certainly a piece of cake for a supreme being. In fact, the Amazing Randi has been offering $1 million to anyone who can prove a supernatural power. No one has yet come close to winning it.
What's so improbable about it? We're here, aren't we? That makes it a certainty in my book. There are 200 billion stars in the Milky Way Galaxy alone. At odds of a billion to one against the formation of habitable planets, there would likely be 200 such planets in this galaxy alone. Astronomers estimate that there are more galaxies in the universe than the total number of humans who have ever lived on the Earth! Even if there were only one habitable planet in each galaxy, or one for every ten galaxies, or one per hundred, the probability of at least one habitable planet forming is astronomical! Literally!Yes, it is highly improbable that the Ten Commandments really are the Word of God. But isn't the reality of existence itself so highly improbable that even divine interference seems no less unlikely?
No, I still maintain that those who profess a belief in a supernatural being, whether divine or otherwise, are the ones making the extraordinary claim, and are therefore the ones who must provide the proof for those claims. Without that proof one might just as well claim that Santa Clause created the universe. There's just no way to prove that he didn't.