Cl⁻
Cr³⁺
Mn²⁺
MnO₄⁻
The strongest oxidizing agent is the one with the highest standard reduction potential (E°). From the given data:
E°Cr³⁺/Cr = -0.74V
E°MnO₄⁻/Mn²⁺ = 1.51V
E°Cr₂O₇²⁻/Cr³⁺ = 1.33V
E°Cl/Cl⁻ = 1.36V
Comparing the reduction potentials, MnO₄⁻ has the highest positive value (1.51V). Therefore, MnO₄⁻ is the strongest oxidizing agent among the given options.