Tsar Nicholas I put down the Decembrist Revolt in 1825. In this revolt, Russian army officers led abot 3000 soldiers in a protest against the Tsar's assumption of the throne after his elder brother Constatntine removed himself from the line of succession.
Alexander II was assassinated in 1881 during a bomb attack by the revolutionary movement Narodnaja Volja.
Alexander III began a program of Russification because he believed that remaining true to Russian Orthodoxy, Autocracy, and Nationality would save Russia from revolutionary agitation. All cultures and nationalities within the Russian empire should be wiped out and alle the people within the empire should become 'Great Russians'.
Tsar Nicholas II was the son of Alexander III and would be the last Russian Tsar. Following the February Revolution of 1917, Nicholas and his family were imprisoned. Eventually he and his family were murdered by their Bolshevik guards on the night of 16 and 17 July 1918.