It is very difficult to tell in an objective way who is and is not a dictator. Therefore, different scholars will label different Mexican leaders as dictators.
The one Mexican leader who is accepted by essentially all scholars as a dictator is Porfirio Diaz. Diaz essentially ran Mexico from 1876 until his rule was ended by the Mexican Revolution in 1911. However, there are two previous Mexican leaders who are labeled as dictators by some historians. These are Augustin de Iturbide and Manuel Lopez de Santa Anna. Iturbide was officially the “Emperor” of Mexico right after it became independent. He reigned for less than a year. Santa Anna was ruler of Mexico on and off from the 1830s through the 1850s. Both men were autocratic, though there is disagreement as to whether they had the complete control necessary to call them dictators.