Which Russian ruler, born in 1530 and died in 1584, became notorious for his cruelty?

Czar Boris III brought which Balkan country into World War II on the Axis side? Boris Karloff was wrapped in bandages as a revived Egyptian in which 1932 horror film? Which conquistador, born in Spain in 1485, toppled the Aztec Empire and died in Spain in 1547? Which king, born in 1491, married in 1509, 1533, 1536, twice in 1540 and again in 1543? Which Russian czar, who lived from about 1551 to 1605, inspired a drama by Pushkin and an opera by Mussorgsky? Who married 18-year-old William Shakespeare in 1582 and died in 1623? Which Dutch painter, born in 1606 and died in 1669, painted "The Anatomy Lesson of Dr. Tulp"? Born in Woolsthorpe, England, in 1642, which scientist supposedly had a dog named Diamond that set fire to his papers?