He refuses to be part of the system he set up. In the middle of an argument, Ralph tries to remind Jack of the rules that he (Jack) first suggested. "Because the rules are the only thing we've got!" "You're breaking the rules!" "Who cares?" Ralph summoned his wits. He expects others to stick to the rules but does not see the need to do so himself. When it suits him, Jack ignores the rules or makes up new ones to suit his purpose. The mask seems to turn him into something else - a dancing, leaping savage whose laugh becomes the growling of an animal. Jack has been painting his face with war paint to make him look even more menacing than he already is. He capered toward Bill, and the mask was a thing on its own, behind which Jack hid, liberated from shame and self-consciousness. He began to dance and his laughter became a bloodthirsty snarling. Throughout the novel he gradually turns into a real savage with no sense of justice or what is right. He is a cruel bully and picks on those who are weaker than himself. Right from the start, Jack has a savage nature. Jack is an unlikeable character, motivated by evil and whose bad traits only get worse as the story progresses. By the end of the novel, he is ordering the torture of other boys and even tries to organise the murder of Ralph. Jack eventually forms a breakaway group of his own and swiftly becomes a violent dictator. Although he hesitates to kill the first pig they come across, it is not long before Jack is able to do so at which point other boys start to follow his ways.
It is noteworthy that Jack has a knife with him which he produces in one of the first conversations with Ralph.
Jack is clearly used to getting his own way and is a bully - he uses verbal and physical violence when necessary.
It is no wonder that he is annoyed when Ralph is elected leader above him. When Jack first appears he is already in a position of authority as he is the Head Boy of his school and lead chorister. Jack has red hair and freckles and is tall, thin and bony.