The Athenian Greeks referred to Draco, Solon, and Cleisthenes, for example, as tyrants because the normal functioning and powers of government were suspended and given to one man to solve a specific crisis. The Romans did the same thing, but used the term dictator, for Cincinnatus, Sulla, and Julius Caesar, with varied results. However, both of those terms today mean something completely different, and not in a good way.
I don't mind referring to Napoleon as an absolute monarch/ruler, or even the more accurate enlightened despot, which are both terms applicable to the time in which he ruled, and certainly more accurate. An enlightened despot, like Joseph II, has the power to declare war, make peace, issue laws, and so forth and so on. So does an absolute autocrat like Alexander I.
My only issue here is co-opting a 20th century term with its 20th century baggage and applying it to an early 19th century ruler, especially when there are historically correct terms that convey the same sense of "absolute power," as well as the power to declare war you seem so fond of citing as the hallmark of a "dictator." It was a hallmark of an absolute monarch/enlightened despot/autocrat too.