Higher the electrode potential, better is the oxidising agent. Since, the electrode potential decreases in the order :
$Ag^{+} \left|\,Ag \left(+0.80 \,V\right) \,>\,Fe^{3+}\,\right|\,Fe^{2+}\,\left(+0.77\,V\right)\,>$
$I_{2\left(2\right)}\,\left|\,I^{-}\left(+0.54\,V\right)\,>\,Cu^{2+}\,\right|\,Cu\,\left(+0.34\,V\right)$
Hence, Ag is the strongest oxidising agent.