difícil de aplacar
From LSJ
ταῦτα δὲ ἔδει ποιῆσαι κἀκεῖνα μὴ ἀφιέναι → these things should have been done without neglecting the others | these are the things you should have done without neglecting the others | these ought ye to have done, and not to leave the other undone
Spanish > Greek
δυσεξίλαστος, δυσμείλικτος, δύσπαυστος, δυσδιάλυτος, δυσπαρηγόρητος