Ivan the Terrible was the first Tsar (emperor) of Russia, having originally been it's Grand-Prince but having himself crowned Tsar to grow in power. While the nickname of The Terrible is accurate in describing Ivan, it is actually a mistranslation of his actual nickname Ivan Grozny which roughly meant "Ivan the very scary and dangerous".
Ivan was a cruel and brutal dictator who was ruled by amoral machievellian nobles known as Boyars following the death of his father the Grand Prince and his mother (who was likely killed by the Boyars). After getting coronated, Ivan exextuted several boyars in order to set an example and proceeded to turn Russia into an empire which he involved in several poorly thought out wars which would last the rest of his rule, weakening Russia. Ivan is known for having been a cruel dictator who had his own equally cruel secret-police which enforced his rule from the shadows. In 1581 Ivan accidentally murdered his own son Ivan Ivanovich after Ivan the Terrible attacked his son's wife. Ivanovich spoke out against his father's actions leading Ivan to hit his son over the head with a club in anger, accidentally killing him.
Ivan the Terrible died in 1584, apparently out of anger for having lost a game of chess although some historians believe this could have been the cover up story for a boyar-lead assasination.