One example is the Wrathful in the mud, that so angers Dante. A Wrathful soul is one who showed only cruelty, no compassion or pity in his lifetime. The trapped soul in the mud does not draw Dante's pity-and this is fitting since the wrathful is receiving the same treatment he was guilty of.
Another example is that of Phlegyas. Phlegyas burned Apollo's temple down because Apollo was in love with his daughter. For this, Apollo killed him and condemned him to Hades. It is appropriate that he was appointed an oarsman between the Wrathful and the Impious souls.