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
EMn3+/Mn2+0=+1.57VETi3+/Ti2+0=−0.37VEFe3+/Fe2+0=+0.77VECr3+/Cr2+0=−0.41V
As we can see Mn+3 has the highest value of standard reduction potential, so it will be the strongest oxidising agent.