What lie did Jack tell the others at the assembly in Chapter 8?
When Jack initially takes the conch and addresses the group of boys in chapter 8, he begins by mentioning that they saw the beast on the top of the mountain. He then lies to the boys by telling them that the beast is a hunter and says that Ralph called the hunters "no good." Both comments are lies because Jack could not have told whether or not the beast was a hunter and Ralph never said the hunters were no good.
Earlier in chapter 8, Ralph referred to the hunters as "boys armed with sticks" in order to convey the fact that Jack's hunters would not be capable of killing the menacing beast. However, Jack spins Ralph's words in hopes of damaging his reputation. Jack continues to lie to the boys by saying that Ralph thinks they are cowards and even mentions that Ralph did not go to the top of the mountain. Both of Jack's statements are lies, and Ralph did climb to the top of the mountain with Jack and Roger. Jack's initial attempt to usurp power fails and he quits Ralph's group.
Jack calls an assembly in chapter 8 after Ralph, Jack, and Roger see the "beast" at the top of the mountain. He begins by telling the group of boys that they have seen the beast and that they couldn't kill it. Jack then immediatley begins to criticize Ralph by saying that Ralph thinks the "hunters are not good" and that Ralph thinks they are cowards. Jack tries to undermine Ralph's authority and position as cheif by telling the boys that Ralph is actually the coward because he was too afraid to go with Jack and Roger to the top of the mountain, which is a lie. In fact at the end of chapter 7, when the boys were on the top of the mountain, Ralph was hesitant at first, but he was the one who stood up and "took two leaden steps forward" toward the beast.
Jack lies to the boys because he realizes that he does not have as much power as Ralph, and he wants to make Ralph look bad in front of the other boys. Jack wants the boys to respect him more than Ralph.