Explanation: The Russian Empire under the Tsars continued serfdom later than any other major European country - some 23 million people in the Empire were still serfs when they were freed... in 1861.
For obvious reasons, this enduring legacy of near-slavery did no favors to the long-term stability of the monarchy, and Russia similarly lagged behind its peers economically in part because of the long-lasting effects of keeping an entire nation in bondage.