In "A Good Man is Hard To Find", did the grandmother know too much about the past, and is that the reason why the Misfit killed her?
The Misfit says directly: "it would have been better for all of you, lady, if you hadn't of reckernized me." That seems to imply that maybe he would have not killed them, if he had been recognized by her. However, even before this he was creepy, telling the mother to call the "children to sit down by you? Children make me nervous. I want all you all to sit down right together there where you're at." He could just honestly be nervous around kids, or, be controlling the situation to his designs. When Bailey says he can fix the car, the Misfit says that's great, but "first you and Bobby Lee get him and that little boy to step over yonder with you", telling him to take the family into the woods, where they are shot. It is almost as if the accident was secondary to his decision. The car being fixed had no impact; he had already decided. Later, he admits, "I found out the crime don't matter. You can...kill a man or take a tire off his car, because sooner or later you're going to forget what it was you done and just be punished for it." This seems to indicate that doing good doesn't matter to him. Plus, he needed a shirt, and children made him nervous; it seems reason enough for them to kill the family. Overall, the story seems to indicate that he was hopeless enough that her recognizing him might have added to his intentions, but not been a catalyst for them.