Complex sentence: Of all the ancient Greeks, Aristotle was perhaps the most influential promoter of the concept of "oriental despotism"; his student, Alexander the Great who conquered Persia, ruled by the "despotic" Darius III last king of the Achaemenid dynasty.
Split into simpler sentences: Of all the ancient Greeks, Aristotle was perhaps the most influential promoter of the concept of "oriental despotism". He passed this ideology to his student, Alexander the Great, who conquered Persia, which at the time was ruled by the "despotic" Darius III, the last king of the Achaemenid dynasty.