Lithium (\( Li \)) has the highest standard reduction potential, making it the strongest oxidizing agent: \[ E^\circ_{\text{Li}} = -3.04 \, \text{V}. \]
Explanation: \( Li \) easily loses its single valence electron, making it highly reactive.
Other elements like \( Cu \), \( Al \), and \( Mg \) have lower oxidizing potentials.