The infamous tsar of Russia known for his oppressive reign was Ivan IV, commonly referred to as Ivan the Terrible. Reigning from 1547 to 1584, he transformed Russia into a multiethnic and large empire. However, his rule was marked by significant brutality, including the establishment of the Oprichnina, a state policy characterized by mass executions and the repression of dissent. His later years saw a descent into paranoia and erratic behavior, leading to widespread fear. Ivan's legacy is complex; while he made significant contributions to the centralization of power in Russia, his tyranny and violence left a lasting scar on Russian history.