Who is last to go over to Jack's tribe?

At this point, we've reached chapter 11 of Lord of the Flies. Jack is now in complete control of the island, lord and master of all he surveys. As his power has grown, so Ralph's has gradually ebbed away until he is left isolated, his band of followers sorely depleted. Without Piggy's glasses it is impossible for Ralph and his group to light a fire. There's nothing for it; they will have to undertake a dangerous mission to enemy territory. So they go to Castle Rock, Jack's impregnable fortress, to try and make the enemy see sense.
But not surprisingly, Jack is in no mood for compromise. He and Ralph get into a fight, which only ends when Roger casts down a huge rock from above. The rock strikes Piggy, and he falls to his death on the rocks below. Piggy was holding the conch shell, which has now been shattered. This is deeply symbolic because the shell represents rules-based authority. Now that Jack is in charge, presiding over a savage reign of terror, all such authority has been completely destroyed. Ralph takes to his heels and escapes to the jungle. Jack and Roger set about torturing Sam and Eric, who then have no choice but to become the last of Ralph's followers to join Jack's tribe.