с трудом поддающийся очищению

From LSJ

ἀγαθοὶ δὲ ἐγένοντο διὰ τὸ φῦναι ἐξ ἀγαθῶν → they were virtuous because they were sprung from virtuous men, virtuous they were because they were sprung from men of virtue

Source

Russian > Greek

δυσκάθαρτος