[Please note that literature is open to a great many interpretations. Responses to this question, therefore, are subjective.]
In Flannery O'Connor's short story "A Good Man Is Hard to Find," the two most important traits that the Misfit has are his calm demeanor and his childlike defenselessness. This is not to say that these are good traits—but they function in a fascinating way in the story.
The first surprises the reader in trying to reconcile his relaxed attitude with the brutality of his actions. Closely connected to this is the necessity for the reader to recognize that the gentleness that often accompanies serenity is not there, even though we might be tempted to believe better of him than he deserves. When they all meet, there is something almost gentle about the Misfit.
With the second trait, his child-like vulnerability, the reader catches glimpses of the wounded child, which allows insight of unexpected depth into this seemingly one-dimensional character. The glimpse is all the more disturbing when the Grandmother calls him "one of my babies."
The Misfit's demeanor makes him more frightening and, consequently, more lethal than someone who is overtly angry. Someone who displays strong and negative emotions prepares the reader for the kind of brutality in which he might engage. His polite regard for them might at first begin to garner in the reader sympathetic feelings toward him.
Bailey turned his head sharply and said something to his mother that shocked even the children. The old lady began to cry and the Misfit reddened.
"Lady," he said, "don't you get upset. Sometimes a man says things he don't mean. I don't reckon he meant to talk to you thataway.
Bailey says something so terrible to his mother that his children are shocked and the Grandmother begins to cry. Ironically, it is the Misfit's face that turns red. It could be out of anger, but his peaceful manner seems to infer that he is embarrassed by Bailey's behavior. He then tries to calm the Grandmother, explaining that Bailey probably didn't mean what he said.
What we see and what we hear are at odds with each other. For in the next sentence, the Grandmother gets slightly hysterical, imploring the Misfit to assure her that he wouldn't kill a lady.
His ability to do just that is reflected in response:
I would hate to have to.
He does not say "no." It is also noteworthy that for monster he is, he is honest. Certainly he has nothing to fear carrying a gun, but he could simply remain silent or ignore them all. He maintains a sense of tranquility as he carries on a discussion with the Grandmother. All the while, he arranges that their car will be fixed, and the members of the family are moved off into a wooded area and systematically disposed of. His composure becomes more frightening (if possible) as he has the other women and the baby killed. We are chilled to the bone to hear him say, "No pleasure but meanness."
The Misfit at times seems child-like and helpless. When he speaks of why he is in jail and why he has taken the name "Misfit," we learn that he thinks he has been jailed and punished for things he never did. With deep irony, he says that he and Jesus are alike in that way. Jesus had committed no crime, and the Misfit didn't believe he had either, but the authorities had papers stating that he had. He displays a sense of helplessness in that he never saw the papers with the charges against him and cannot remember doing anything wrong. This sense of injustice troubles him, as it would a child.
The Misfit also struggles with who he has become. He wishes he had been alive at the time of Jesus so he would now know that to believe...
It ain't right I wasn't there because if I had of been there I would of known...I wouldn't be like I am now." His voiced seemed about to crack...[and he looked] as if he were going to cry...
The Misfit says, "God never made a finer woman than my mother." He also says that his father had a heart as good as gold, but then notes that his father had a way of not getting in trouble with the law, inferring that his father was a nefarious character of some sort. The Misfit shares that he was charged with killing his father, but that it cannot be true because his father died of fever. He appears to take honesty very much to heart, but then we wonder if the authorities were wrong or if the Misfit is insane. Certainly something has damaged the psyche of this man.
At the very instant the Misfit looks so sad, the Grandmother does two things that galvanize the plot forward with the suddenness of a lightning bolt. With a gentle voice the Grandmother says:
Why you're one of my babies. You're one of my own children!
She reached out and touched him on the shoulder. The Misfit sprang back as if a snake had bitten him...
The Misfit's traits of polite gentleness and child-like helplessness are like the swaying of a cobra: the movement fascinates the intended victim, taking his or her mind off of the present danger. However, despite its mesmerism and grace, the snake still attacks, killing the person it had so recently captivated.
These character traits are the two most important because they show how calmly vicious the Misfit can be, while also confusing the reader when he allows the damaged child to show.