Note that there is a difference between combat skills and capability in combat. When Slade and Batman first fought in Deathstroke’s comic, the mercenary bested Batman, But Slade said that Batman had better fighting skills and that the only reason he (Slade) won was because he had a superior physiology. So, just because Slade can beat someone, that doesn’t mean the loser has worse fighting skills than Deathstroke.
