Both Endless Space and Civ6 have broken AI, though I admit Civ6 is in the class of its own.
AI in general is the main reason why Galactic Civilizations II and III are my favorite space 4X games. Not that it's perfect mind, but at least the other races act in a believable manner according to each races traits, diplomacy and player actions. That and the fact there are no predefined "lanes" between systems, you can move your ships freely across the map.