Can you see in every person a beast? Also in Simon?
Every person has the capacity to be good and the capacity to be evil. That is the basis of this novel. In each of the characters there are good qualities. But the beast is seen in a couple of the boys more so than others. Jack is the obvious choice for one of the evil boys. Roger is another character who can be viewed as even more evil than Jack. He is the "executioner" who uses his weight to free the boulder that kills Piggy. He is also the "strong arm" for Jack when he has his "tribe" established.
The boys who follow Jack's tribe and become part of it all have the beast within them as well. They are all willing to kill Ralph in the end. The characters who are good and don't show signs of "the beast" are Simon, who is the Christ symbol in the book; Piggy, who represents intelligence and common sense; and Samneric (the twins) don't ever willingly go along with Jack, but are captured by him and his hunters. Ralph most likely has the capacity for the beast but he controls it. I'm sure he desires bad things to happen to Jack and his tribe, but he would only hurt them to save himself. The possibility is there, though.