Strongest Reducing agent → which undergoes oxidations

Mn⁺² $\underset{}{\overset{}{\to }}$ MnO4^¯ + 5e^¯             ${\mathrm{E}}_{{\mathrm{Mn}}^{+2}/{\mathrm{MnO}}_4¯}^{\mathrm{o}}=-1.51\mathrm{V}$      

2Cr³⁺ $\underset{}{\overset{}{\to }}$ Cr₂O₇^2– + 6e^¯          ${\mathrm{E}}_{{\mathrm{Cr}}^{+2}/{\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}}^{\mathrm{o}}=-1.33\mathrm{V}$      

2Cl^¯ $\underset{}{\overset{}{\to }}$ Cl₂ + 2e^¯                    ${\mathrm{E}}_{\mathrm{Cl}¯/{\mathrm{Cl}}_2}^{\mathrm{o}}=-1.36\mathrm{V}$

Cr $\underset{}{\overset{}{\to }}$ Cr⁺³ + 3e^¯                      ${\mathrm{E}}_{\mathrm{Cr}/{\mathrm{Cr}}^{+3}}^{\mathrm{o}}=0.74\mathrm{V}$

E° (+ve) or $∆$G (–ve) represents spontaneous process