δυσαποτέλεστος
From LSJ
γλυκύ δ᾽ἀπείρῳ πόλεμος, πεπειραμένων δέ τις ταρβεῖ προσιόντα, νιν καρδίᾳ περισσῶς → A sweet thing is war to the inexperienced, but anyone who has tasted it trembles at its approach, exceedingly, in his heart (Pindar, for the Thebans, fr. 110)
English (LSJ)
ον,
A hard to accomplish, Eust.1956.18.