There was no Tsar that overthrew Nicholas 2 in 1917, the people rebelled and he abdicated
Czar's are similar to kings or emperors. They can improve the land they rule or hurt the citizens living there.
The term Czar was given to the leader of Russia. He was a king but was called the Czar.
Nicholas the first was Emperor of Russia from 1825-1855. In his capacity he was also king of Poland and Grand Prince of Finland
1861