Step 1: Understanding the Concept:
This question asks to identify the Russian ruler who ended the system of serfdom.
Step 2: Detailed Explanation:
\[\begin{array}{rl} \bullet & \text{Serfdom, a system where peasants were tied to the land and the nobility who owned it, was a major social and economic issue in Russia for centuries.} \\ \bullet & \text{The abolition of serfdom was accomplished by Czar Alexander II through his Emancipation Manifesto of 1861.} \\ \bullet & \text{This monumental reform earned him the title "Alexander the Liberator".} \\ \bullet & \text{Lenin, Stalin, and Trotsky were figures from the later communist era, long after serfdom had been abolished.} \\ \end{array}\]
Step 3: Final Answer:
Czar Alexander II abolished serfdom in Russia.