In one passage the 11th century Eastern Roman scholar Michael Psellos wrote about how no leader could ever actually be perfect:

In one passage the 11th century Eastern Roman scholar Michael Psellos wrote about how no leader could ever actually be perfect: “Was there ever a man, above all, was there ever an emperor who won the crown of praise for all his deeds, without exception?”

“When we look at the great leaders of men, persons renowned for their characters and their words and deeds, men such as Alexander the Macedonian, the two Caesars (Julius Caesar and Augustus), Pyrrhus of Epirus, Epamindas the Theban, Agesilaus the Spartan, not to speak of others who won brief commendation from their admirers, when we look at these men, we do not find in their lives an equal balance of virtue and vice, as we know from their biographers, but generally they incline somewhat to the worse.” Great men who accomplish great things often have serious flaws, as we know. 

An interesting aspects of this is that Psellos uses this passage to soften a comparison to the Emperor Constantine IX Monomachos: “When I compare this very great emperor with them, I am aware that is inferior in bravery, but he is a finer man than they when one considers the other good qualities, and his superiority here is just as marked as theirs is in the first case…” Essentially, he was arguing that those great men had terrible vices which Constantine Monomachos did not, that he was a great person. As always from Psellos, an intelligent way to praise the emperor.

We can all learn from great men in history and admire their achievements, but we should never pretend they were perfect either. Sometimes what makes a great ruler and a great person are totally different. 

Source: Fourteen Byzantine Rulers also known more properly as the Chronographia of Michael Psellos