pernicioso
From LSJ
τὸ γὰρ εὖ πράττειν παρὰ τὴν ἀξίαν ἀφορμὴ τοῦ κακῶς φρονεῖν τοῖς ἀνοήτοις γίγνεται → undeserved success engenders folly in unbalanced minds
Spanish > Greek
βλαβερός, ἀνήκεστος, δηλητηριώδης, δηλητήριος, δηλήεις, ἀξιώλεθρος, ἀλεγεινός
