ἄστρεπτος
From LSJ
Τὸ νικᾶν αὐτὸν αὑτὸν πασῶν νικῶν πρώτη τε καὶ ἀρίστη. Τὸ δὲ ἡττᾶσθαι αὐτὸν ὑφ' ἑαυτοῦ πάντων αἴσχιστόν τε ἅμα καὶ κάκιστον. → Τo conquer yourself is the first and best victory of all, while to be conquered by yourself is of all the most shameful as well as evil
English (LSJ)
ον,
A without turning the back, Theoc.24.96. Adv. ἀστρᾰτηγ-τεί AP7.436 (Hegem.). 2 unbending, rigid, δόγμα ib.103 (Antag.), cf. 6.71 (Paul. Sil.); τὸ θεῖον Max.Tyr.11.3. II whence none return, Ἅιδης Lyc.813.