Kural - 773

Fierceness in hour of strife heroic greatness shows;
Its edge is kindness to our suffering foes

Explanation
The learned say that fierceness (incontest with a foe) is indeed great valour; but to become a benefactor in case of accident (to a foe) is the extreme (limit) of that valour.

Tamil Transliteration
Peraanmai Enpa Tharukanon Rutrakkaal
Ooraanmai Matradhan Eqku.