All empires are to some degree evil because their agenda is to dominate weaker peoples and nations. They almost all committed crimes against humanity and genocides if you look retrospectively from the todays point of view. Even our beloved Roman Empire that the Western civilization is built upon was genocidal empire.
Not sure if we can call it "beloved". For sure respected for what it did to build the base of modern civilization, but we are aware of its dark sides. And probably Nero would be an excellent example of what can happen to the empire and its people when a crazy person becomes its ruler.