ἀνάγκᾳ δ' οὐδὲ θεοὶ μάχονται → but not even gods fight necessity (Simonides, fr. 37.1.29)
P. and V. δυσχερής, ἄπορος, ἀμήχανος (rare P.), προσάντης, V. δυσπετής, Ar. and P. χαλεπός.
of ground: P. and V. τραχύς, P. χαλεπός.
it is difficult to do it: V. δρᾶν ἀμηχάνως ἔχει (Eur., Fragment).