Is there any fictional character more powerful than TOAA (The One Above All)?

Answers

Entropy

God. (yeah, I went there. Fictional).

Ryan

The obvious answer here is Saitama from One-Punch Man, given that his entire gimmick is, of course, that he can beat anyone in a single punch. While he's not faced anyone of TOAA's level (that I know of), Saitama's physical strength is described by many characters to be literally limitless. If he can punch it, he can defeat it, simple as that.