The French Revolution was the most violent revolution of the 18th century. This revolution started in 1789.
By this time, many of the peasants in France owned land and were educated. They wanted to get rid of the feudal system that had been plaguing them with taxes and oppression since the Middle Ages. France was also the most populated nation in Europe, with 26 million inhabitants, and crop failures stopped the population from seeing the king as divinely ordained.
Because of the nation's many wars, the government was forced to tax the people more heavily, and even taxing the noblemen and clergy, who were exempt in other countries.
The middle class (a.k.a. most of the population) didn't like that they couldn't have political power and positions of honor.
These are just a few reasons why the French Revolution started.