Lucian, Phalaris 1.8
The tyrant Phalaris of Acragas is best known for cooking people to death in a novelty bronze bull, but here Lucian makes him point out that you have to be cruel to be kind, it hurts him more than them, etc. etc.
ποσάκις γοῦν ἐδάκρυσα μαστιγουμένων ἄλλων, ποσάκις δὲ θρηνεῖν καὶ ὀδύρεσθαι τὴν ἐμαυτοῦ τύχην ἀναγκάζομαι μείζω κόλασιν αὐτὸς καὶ χρονιωτέραν ὑπομένων; ἀνδρὶ γὰρ φύσει μὲν ἀγαθῷ, διὰ δὲ ἀνάγκην πικρῷ, πολὺ τοῦ κολάζεσθαι τὸ κολάζειν χαλεπώτερον.
How many times have I wept as others are being flogged? How many times have I not been compelled to lament and wail for my own misfortune, as I undergo greater and more chronic punishment than theirs? For a man who is naturally moral, but harsh by necessity, it is much harder to punish than to be punished.