Ralph was the original one to unite the group and was even elected leader, this was his effort to become civilized and try to survive on the island with all these different kids.
Jack is throughout the book, is one of those kids you want to punch, he even hesitates to kill a pig, being one of the last signs of a civilized person that he shows for the rest of the book.
Roger, or pure evil, knows his limitations, and although he is still throwing rocks at kids, he’s not hitting them, because he knows his limitations at this point even though he still wants to do it.
Jack is the main leader, and is being a savage on this island, he helps pull Simon apart, even though they don’t really know it’s him. He also never admits to the crime and abuses the power that he gave himself.
Roger realizes what he is capable of and kills piggy, knowing full well that the rock would fall, and piggy would be no more. Roger no longer has the fear of consequence, losing the civilized part of him.
Ralph is done, and instead of being the bigger person, he fights Jack, acting just like he is, losing the drive to be a more civilized person and referring to violence to finally fix what Jack started.