On the very last page of "The Stranger," Meursault argues with the chaplain and tries to prove the point that Camus has been trying to make during the entire book, the argument of existentialism. He gets very worked up and yells and screams and rants in a climax of frustration at his situation and at society's inability to understand him. Immediately after, he calms down and feels "a wondrous peace" (122.) He talks directly about his mother and relates to her need to connect to another person before she died and "live it all again" (122.)
Meursault experiences a transformation here and I believe that it is the final step to leaving all his human qualities behind. Meursault never had that many human qualities to begin with, and acted more with animalistic tendancies such as his love of simple physical pleasures, his indifference towards religion, his failure to care about relationships and society recognizes that he is not human and that is why they sentence him to death. In the second part of the book, Meursalt's hidden human traits like his fear of trial, anger at the way society views him, and his innocence of the world begin to show. He talks about how he struggles with hope, that he is tortured by the idea that there might be a way out of his hopeless situation. He doesn't want to think that he could escape, or he wants a concrete chance, such as when he describes how a death pill should work "nine times out of ten." This "hope" is a human trait and at the end of the book, Meursault finally lets go of it.
What Meursault loses is his fear of death which is something that all humans have in common. He calls it "opening himself to the gentle indifference of the world" (122.) Until the last page, Meursault cares if he dies. He doesn't want to lose life and he is afraid of death. The fight with the chaplain exhausts him to the point where he loses his fear of death and finally he truly does not care about anything. This is what makes Meursault happy, is to not care about anything and to know that nothing matters. All humans are afraid of death and this means that at the end of the book Meursault is entirely inhuman.
"For everything to be consummated, for me to feel less alone, I had only to wish that there be a large crowd of spectators the day of my execution and that they greet me with cries of hate" (123.)
I interpreted this last sentence to mean that Meursault wins at the end of the novel. If a large crowd greets him with hate when he dies it means that he was not in vain, that his argument was proven true and that he can go to his death without fear, without caring and knowing that he was always right and society was wrong. I think that this is what Camus is trying to prove in the end of "The Stranger" as Meursault sheds his last scrap of humanity and goes to his death the same way that he lived, happy and content.