how does jack have superior power?

Jack is accustomed to being in a position of authority and he is comfortable with giving orders. he expects his orders to be obeyed and is quite willing to use force to punish anyone who disobeys. Jack is quick to make decisions, he is decisive and is happy to lead by example. Jack is also persuasive and passionate about his beliefs, he can be generous, when it suits him and his confidence in his own abilities inspires confidence in his followers. Jack understands what his followers want and need and as he wants the same things too he is usually quite happy to grant most of their wishes, which makes him pretty popular. At the end of chapter 6 Jack is the one with the bravery and guts to lead the boys on a hunt for the beast,

Jack also knows how to capitalize on the boys' fears. He promises to protect them from the Beast, so they admire him and are willing to follow him.

Mostly, Jack sees himself as "above" the other boys, which Ralph does not. Ralph believes that he is leader because he was chosen. That's not enough; he has to earn the boys' respect, and since he doesn't show power by punishing boys who don't do what he says, they lose respect (fear) of Ralph.

Jack is accostumed of power,dominance,and popular.