The best revenge is to be unlike him who performed the injury.

This line is a genuine thought of Marcus Aurelius, drawn from his private notebook, the Meditations, at Book 6, section 6 — where, in the original Greek (Ἄριστος τρόπος τοῦ ἀμύνεσθαι τὸ μὴ ἐξομοιοῦσθαι), he reminds himself that the finest way to answer a wrong is simply not to resemble the wrongdoer. The submitted English — "The best revenge is to be unlike him who performed the injury" — is a smoothed, popular rendering rather than the wording of any one standard translation; the scholarly versions run closer to Collier's 1701 "The best way of Revenge, is not to imitate the Injury" and George Long's 1862 "The best way of avenging thyself is not to become like the wrong-doer." We found no credible rival author and no earlier origin, and the passage sits securely in a primary work he wrote to himself in the 170s AD, so the attribution is sound. The one caveat a careful reader should keep in mind is that the exact phrasing here is a paraphrase in circulation, not the verbatim line of a named translator. In substance and location, however, it is authentically Marcus Aurelius.