HECUBA: It the duty of a good man to do good everywhere and always to punish the evil men.

[ἙΚΆΒΗ: ἐσθλοῦ γὰρ ἀνδρὸς τῇ δίκῃ θ᾿ ὑπηρετεῖν
καὶ τοὺς κακοὺς δρᾶν πανταχοῦ κακῶς ἀεί.]

Euripides (485?-406? BC) Greek tragic dramatist

Hecuba [Hekabe; Ἑκάβη], l. 844ff (c. 424 BC) [tr. Theodoridis (2007)]
    (Source)

Requesting that Agamemnon help her avenge the murder of her son, Polydorus.

(Source (Greek)). Alternate translations:

For the good man's duty
Is to obey the dread behests of justice,
And ever punish those who act amiss.
[tr. Wodhull (1809)]

For it belongs to a good man to minister justice, and always and in every case to punish the bad.
[tr. Edwards (1826)]

For 'tis the good man's part to champion right,
And everywhere and aye to smite the wrong.
[tr. Way (Loeb) (1894)]

This, this is virtue: to do justice still,
Requiting evil every way with ill.
[tr. Sheppard (1924)]

For it is always a good man's duty to help the right, and to punish evil-doers wherever found.
[tr. Coleridge (1938)]

Do your duty as a man of honor:
see justice done. Punish this murder.
[tr. Arrowsmith (1958)]

A good man is just, he'll punish the bad.
[tr. McGuinness (2004)]

A good man commits himself to justice and combats the wicked in whatever place.
[tr. Harrison (2005)]

Do your duty. Mete out justice.
Punish this heinous crime against gods and man.
[tr. Karden/Street (2011)]

For it is right that a good man serve justice
And always do evil everywhere to evil men.
[tr. @sentantiq (2020)]