τὸν αὐτὸν ἔρανον ἀποδοῦναι → pay him back in his own coin, repay him in his own coin, pay someone back in their own coin, pay back in someone's own coin, give tit for tat, pay back in kind
P. and V. χρήσιμος, χρηστός, σύμφορος, πρόσφορος, ἐπιτήδειος, Ar. and P. ὠφέλιμος, προὔργου, Ar. and V. ὠφελήσιμος.
