"A Good Man is Hard to Find" by Flannery O'Connor contains a much deeper sense of evil than "The Short Happy Life of Francis Macomber." Although both short stories address the topic of murder, guilt, and any number of deadly sins, "A Good Man is Hard to Find" strikes the reader as much more problematic because of the depraved nature of the killings committed by the Misfit. He murders an entire family on a whim, and despite O'Connor's slight allusions to redemption through his conversation with the grandmother, the Misfit strikes the reader as a truly sadistic character.
"The Short Happy Life of Francis Macomber" also ends in violence with the questionable accidental shooting of Francis by his wife Margaret. Wilson cruelly blames her for murdering her husband, because he suspects that Francis may have found enough gumption to divorce her. Unlike the Misfit, Margot does not come across as a cold-blooded killer. Hemingway leaves her motives undefined--she very well could have been taking aim at the buffalo to save her husband; moreover, if she really had been trying to kill him on purpose, she would have had to had amazing aim to pull that shot off deliberately.
O'Connor leaves the reader with absolutely no doubts as to the bloodthirstiness of the Misfit or his dark compulsions. He may have seen the potential for redemption in the grandmother's words, but he killed her anyway.