ἀνατρεπτικός
From LSJ
Ζῆν οὐκ ἄξιος, ὅτῳ μηδὲ εἷς ἐστι χρηστὸς φίλος → Life is not worth living if you do not have at least one friend.
English (LSJ)
ή, όν,
A turning upside down, upsetting, ἐπιτήδευμα . . πόλεως ὥσπερ νεὼς ἀ. Pl.R.389d; στομάχου Dsc.2.70; of the pulse (dub. sens.), Gal. 8.928, cf. 644; οἱ ἀ. διάλογοι Plato's refutative dialogues, as 'Euthydemus' and 'Gorgias', Thrasyll. ap. D.L.3.59, cf. Hermog.Meth. 10.