Roger and Jack are very similar in Lord of the Flies. Both demonstrate an affinity for violence. Roger early on reveals his predilection for bullying when he carefully throws the stones at Henry on the beach; he seems to genuinely enjoy and find pleasure in willfully hurting others. Jack's violent tendencies progress differently than those of Roger's on the island. At first when given an opportunity to kill a piglet, Jack fails to do so, because he is squeamish about the blood. Later, Jack overcomes his trepidation and embraces his savage side that wearing the painted mask has revealed in him.
One main difference between Roger and Jack is their motives for using violence. Jack links violence and fear to control, whether in hunting or making the other boys follow his lead. He uses fear and the threat of violence to maintain his superiority in the tribe. The perfect example of this is when he has Wilfred tied up for no apparent reason to beat him, except to make a public example out of the boy and assert his own power within the tribe. Jack also connects using violence to strategy, as when he points out using the boulder to crush an enemy to Ralph upon their first visit to Castle Rock. Roger, on the other hand, is really only violent because he enjoys the violence and the power derived from it. Again, the scene with Henry indicates his enjoyment of torture and bullying as well as other more infamous scenes in the book, like the slaughter of the sow in chapter eight and Piggy's death.