Good question. What IS he going to do to Superman? Punch him to death? How hard does he hit? What, in movie damage terms, might you compare Kurse's punches to? Each fist is like having car thrown at you? Each punch is like being hit with a 10 ton safe? Perhaps each punch is like being hit by an exploding locomotive? Impressive strength if we assign him that.
But then again he is Formindable with a capital F. So perhaps each blunt force hit of his fist is like being hit with... A Mountain?