ἀνυπέρβλητος
From LSJ
ἐν ταῖς ἀνάγκαις χρημάτων κρείττων φίλος → it is better in times of need to have friends rather than money, a friend in need is a friend indeed (Menander, Sententiae monostichoi 143)
English (LSJ)
ον,
A not to be surpassed or outdone, φιλία X.Cyr.8.7.15; ἀρετή Isoc.4.71; φιλοτιμία D.2.18; εὔνοια Lycurg.101; ἄνθρωπος ἀ. εἰς πονηρίαν Antiph.168.5; τάχη Epicur.Ep.1p.10U. Adv. -τως Arist. Rh.1370b31, Pyth.Sim.144. 2 persistent, obstinate, of disease, Gal.13.61.