CGT (General Workers Confederation) is the union that, with the help of the Communist Party, broke up the largest-ever strike in history. In 1968, students first, then workers, began to protest. The movement gathered steam until millions were on strike. Workers took control of workplaces, de Gaulle fled to Germany, and France was on the verge of another Commune. CGT, the largest union, either corrupt or merely afraid it was losing control of the workers, broke the strikes up into localized individual ones and urged the workers to hand the factories over to the capitalists and vote socialist in the next election. Tragically, that is what happened. The Communist Party of France, then quite powerful, was still tied to the USSR and was deeply troubled that they'd lost control. Moreover, they were terrified by "Les MAT" as they were called, who were reorganizing the workplaces and were urging workers not only to resist the government but the unions and Party as well. Les MAT (Maoists, anarchists, and Trotskyists) had won the workers over, and the communists were losing power.
After the revolt was over, the government, some say with the help of the unions and Communist Party, conducted a huge Stalinist purge of Maoists, anarchists, Trotskyists, and others who led the rebellion.
As the workers were fond of saying, "In France, you cannot do anything without the Communist Party, and you can't do anything with the Communist Party."
Much has been said and written about the betrayal of the workers by the CGT and the Communist Party, I don't have anything to add save that there is a lesson in all this. The communists destroyed their rivals, but after the fall of the USSR they too waned. Now they are insignificant in French politics.