ῥεῖα δ' ἀρίζηλον μινύθει καὶ ἄδηλον ἀέξει, ῥεῖα δέ τ' ἰθύνει σκολιὸν καὶ ἀγήνορα κάρφει → easily he humbles the proud and raises the obscure, and easily he straightens the crooked and blasts the proud (Hesiod, Works and Days 6-8)
pack ass: Ar. κάνθων, ὁ, κανθήλιος, ὁ, P. ὄνος κανθήλιος, ὁ.
as term of reproach: use fool.