If the half cell reaction $\mathrm{A}+{\mathrm{e}}^{-}\to {\mathrm{A}}^{-}$ has a large negative reduction potential, it follows that ${\mathrm{A}}^{-}$ is readily oxidised as negative ${\mathrm{E}}_{\mathrm{R}\mathrm{P}}^{\mathrm{o}}$ means more ${\mathrm{E}}_{\mathrm{O}\mathrm{P}}^{\mathrm{o}}$ , i.e., more is the tendency to get itself oxidized.