The substance which will have the highest value of reduction potential will be the strongest oxidising agent. The values of reduction potential are as follow

$\begin{array}{r}{\mathrm{E}}_{{\mathrm{Mn}}^{3+}/{\mathrm{Mn}}^{2+}}^0=+1.57\mathrm{V}\\ \\ {\mathrm{E}}_{{\mathrm{Ti}}^{3+}/{\mathrm{Ti}}^{2+}}^0=-0.37\mathrm{V}\\ \\ {\mathrm{E}}_{{\mathrm{Fe}}^{3+}/{\mathrm{Fe}}^{2+}}^0=+0.77\mathrm{V}\\ \\ {\mathrm{E}}_{{\mathrm{Cr}}^{3+}/{\mathrm{Cr}}^{2+}}^0=-0.41\mathrm{V}\end{array}$

As we can see ${\mathrm{Mn}}^{+3}$ has the highest value of standard reduction potential, so it will be the strongest oxidising agent.