I know that Ivan the IV was the first Tsar of all Rus' conquered Siberia and other places, and killed his sons, but weren't such things normal in the 1500's? What made him stand out?
Ivan the Terrible vs. Ivan Grozny is very much a difference lost in translation.
In Russian, the word "grozny" (грозный) is much closer in meaning to words/concepts like "fearsome" or "inspiring awe," and much further away from "bad person" that the word "terrible" implies.