ἀντοφείλειν
From LSJ
αἰὲν ἀριστεύειν καὶ ὑπείροχον ἔμμεναι ἄλλων → always strive for excellence and prevail over others (Iliad 6.208, 11.784)
Greek > English (Woodhouse Verbs Reversed)
(see also: ἀντοφείλω) owe in return
Lexicon Thucydideum
accepti beneficii gratiam debere, to owe thanks for a favor received, 2.40.4.