It is true Corsicans are one of the most important mob groups in France.
They indeed killed a guy named Farid Berrhama (is specialty was barbecues which means he would burn is victims in the trunk of a car).
For the 20 or 30 last years, the corsican mob has been dominated by a group called la Brise de Mer (this was the name of the bar were they would hang out). Members a la Brise de Mer used to be friends, but they divided in the 2000's. One of its members boasted of killing over 50 people.
There was a series called mafiosa about a woman becoming the leader of a corsican gang. Some kind of cheap sopranos...
The fourth season is about her gang taking control of "cercle de jeux" (some kind of casinos) in Paris. Interestingly, two of the actors were involved in the same kind of operation in real life, and were interrogated by the police.
The murder rate seams higher than in amercican mob, but not the same level as italian mob.
Sorry for my English I am French did the best I could.