Explain how the title “Revelation” could actually apply to ALL of O’Connor's stories.

In all—or almost all—of O'Connor's stories, one of her characters has a moment of revelation or illumination, when the grace of God breaks into this person's life and shows a glimpse of God's love or God's mercy or, conversely, a character obtains a glimpse of true evil beneath a "good" facade. Almost always, the characters O'Connor creates are grotesques, people with deep flaws, either inside or out (or both), who have not confronted the deepest levels of either grace or darkness in their lives.
In "A Good Man is Hard to Find," for example, a difficult, manipulative, and racist older woman who has caused her family to be murdered sees the Misfit, the man who has just ordered the death of her family and is about to kill her, through the eyes of love. Through the grace of God, she is able to connect with him for a for an instant before he kills her. That is a moment of revelation for her. Likewise, in "The Artificial Nigger," an ignorant, racist old man named Mr. Head goes to Atlanta with his grandson Nelson and then, out of fear, denies knowing Nelson when Nelson accidentally causes a commotion. Nelson's anger, rejection, and coldness is a form of hell to Head, who experiences a revelation of God's deep mercy when Nelson forgives him. In "Good Country People," Hulga, an educated woman, meets Pointer, a traveling Bible salesman and is unable to see his evil until he tells her he believes in nothing and steals her artificial leg out of spite. At that point, Hulga has a revelation in which she learns that for all her education, she has not before understood pure evil.