insaciable
From LSJ
τὴν οἴησιν ἔλεγε προκοπῆς ἐγκοπήν → he used to say, Opinion forming is the stoppage of progress
ἄατος, ἆτος, ἄβορος, ἄβαρτος, ἀεικενός, ἀκόρεστος, ἀκόρετος, ἀκορής, ἀκόρητος, ἄμαργος, ἄναλτος, ἄπαυστος, ἄπλειστος, ἀπλήμων, ἀπληστόκορος, ἄπληστος, ἀχόρταστος, δυσχαλίνωτος