How does Jack betray himself in Golding's Lord of the Flies?

This is a question that can be answered in many ways.  In Golding's Lord of the Flies, Jack is portrayed as having the most dramatic change.  He begins the novel as the leader of a choir, who can sing C sharp, becomes the formidable leader of the hunters and eventually the tyrannical leader of the entire island, and ends by being reduced to a sniveling red-headed boy.  Because he goes through so many changes, it is difficult to pinpoint when he betrays himself.   At the beginning of the novel, his freckles betray his feelings of mortification when he is not elected chief.  

Later in the novel, he betrays his friend Ralph, but in so doing he betrays himself.  In Chapter 3, Golding writes that 

they look at each other in love and hate.

At first, Ralph and Jack, as the oldest boys on the island, are friends and allies.  Ralph is the chief and appoints Jack leader of the hunters.  But as priorities change, and Ralph becomes more interested in rescue and shelters while Jack becomes more obsessed with hunting, their relationship begins to fracture.  This fracture deepens as the novel progresses so much that Jack leaves Ralph and starts his own group.  But this splinter hurts Jack more than he is willing to admit.  When the boys fail to vote for Jack as chief the second time, Jack actually cries, saying

"I'm not going to play any longer.  Not with you."

Jack needs Ralph's calmness, leadership, sense of fairness, and most of all, commitment to rescue.  When Jack leaves Ralph's group, he hurts himself--ruining his chances of rescue and ruining the boys' chances of keeping the island a safe place.  

Deep down, Jack is afraid.  He does not show his fear often, but he is afraid of the beastie, the unknown, the dark.  When Ralph and Jack get close to what they think is the beastie, it is Jack who runs first.  In fact, Jack has to conquer his fear of killing in order to slay his first beast.  He must become something he is not in order to be a hunter and a killer.  Hence, the face-paint.  Jack must betray, or at least hide, his own identity to become the ruthless leader we see in the latter part of the novel.  

At the very end of the novel, Jack is shown as his true self.  He does not protest when Ralph identifies himself as the boss in answer to the naval officer's question.  Jack knows he is not the true leader.  In actuality, Jack is just a little kid who wanted to be in charge and whose insecurity led him to acts of cruelty and defiance.  In becoming this unscrupulous leader who does not care about the safety or rescue of his tribe, Jack truly betrays himself.