It's commonly asserted that he suffered from incontrollable rage and pathological cruelty, but he seems to me to have been... well, a harsh tsar, but not deranges. The episode with him accidentally beating his son to death doesn't strike me as indicative of anything but the fact that getting into fistcuffs with your dad was a terrible idea, especially if your dad happened to be the king.
Reading material is appreciated too!
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