It could be said that Jean Paul Sartre presents the French vision of Heidegger's vision. For him, existentialism is to explore the consequences of a coherent atheism.
Sartre's philosophy is characterized by an explicitly pessimistic atheism, while human beings, while they need a rational basis for their lives, are unable to achieve it. For Sartre, existentialism is a form of humanism as long as freedom, choice and responsibility remain human.
Sartre will make an ontological distinction between being itself and being for himself, in this way, he will try to establish a difference between man and the world. For while the being itself is what it is, lacking in any relationship, as an undifferentiated mass, refers to the world; the being for itself describes human consciousness in such a way that it is in the world, in the being itself , although it is totally different from it.
The concepts of God and Creation are absurd. God does not exist and therefore all things in the world are contingent because no value is superior to another. Things are meaningless and baseless, and there is no need to find it, while man is a useless passion.
Being for himself is free and condemned to freedom:
“man is now absolutely free. But this freedom is not a gift, but man is condemned to it, condemned because in order for freedom to be full freedom, there can be nothing normatively opposed to man, nor faith in God, nor truths, nor values.” Sartre
Broadly speaking, this is a nihilistic perspective: Man is alone in a hostile world, has no other way out but himself.