κρατίστην εἶναι δημοκρατίαν τὴν μήτε πλουσίους ἄγαν μήτε πένητας ἔχουσαν πολίτας → the best democracy is that in which the citizens are neither very rich nor very poor (Thales/Plutarch)
Use P. and V. ὁ εἰσβάλλων, or use enemy.