Batu Khan

Batu Khan was the grandson of the famous Genghis Khan, and was a strong leader as well. Batu began his European invasion in 1235. Batu and his army were strong fighters, specializing in techniques like feigned retreats and using smoke so his highly skilled archers could shoot their arrows on horseback under cover, Batu and his army were merciless in their conquest. Generally, most feared the Mongol army and would just surrender, but in Kiev they attempted to resisted and the result was terrible destruction described as, "children drowning in the blood of their parents". By 1240 Batu Khan had conquered Russian and was prepared to  take the next step in continuing into Europe. However, at the death of the leader of the Mongol Empire, Batu and his army withdrew saving Europe from what would have been a crushing defeat. Batu Khan created the Golden Horde, essentially a state of the Mongol empire, which provide taxes and tributes to the empire for the next 250 years, lasting from roughly 1240 till around 1502.
Many blame Batu's and the Mongol control for slowing down Russian's progress. Russia, largely cut off from the rest of Europe missed the Renaissance and feeling like they were always behind the times. This leads to Russia missing early aspects of industrialization, and instead remaining largely agricultural. It also lead to a stronger reliance of the Russian Orthodox Church, as new, controversial ideas took much longer to spread to Russia.