What does Jack Merridew represent in Lord of the Flies? The 'little-uns'? Piggy and Ralph?

In Lord of the Flies, Jack represents the savagery or evil
in man. He loses his ability to remain civilized while he is stranded on the island. He
gives in to his innate savagery and becomes dehumanized. He becomes a wretched evil
person. He becomes blood thirsty and slaughters pigs unmercifully. He laughs and shakes
the blood from his hands after killing a sow. He laughs as Roger probes the sow's anus
with his spear. Jack laughs as Roger twists and puts all of his weight on the spear
while the sow screams in agony:

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Jack begins to rub the blood on his hands onto
Maurice, and then they notice Roger withdraw his spear. They become hysterical because
he had pinned the sow by driving the spear through its anus. They reenact the slaughter
until they grow tired.

Then,
Jack hangs the sow's head on a stick to represent the Lord of the Flies. He becomes
cruel in his killing of the sow. Then he leads his mighty hunters into a hunting-dance
frenzy. During the dance frenzy, Simon comes crawling out of the woods and Jack and his
hunters jump on him and kill him with their bare hands and teeth. No doubt, Jack
represents the most evil nature a man can have--a complete lust for blood and the power
of the hunt:

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He represents leadership by intimidation and
rebelliousness. By the end he is compared to an “ape” and called a
“savage.”

Ralph, Piggy and
the littluns represent innocence. They are the good that is found in mankind. They
despise Jack's and his blood thirsty hunters' actions. Ralph and Piggy try to keep order
on the island, but it is hopeless to change Jack and his hunters. In particular, Ralph
tries to get everyone to build shelters and a fire to quicken their
rescue:

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[Ralph] is elected leader and initiates necessity
to build shelters and a fire. He represents leadership by common sense and governmental
authority.

Ralph and Piggy
represent sense and order in all the chaos created by Jack and his hunters. Piggy dies a
senseless death at the hand of Roger who is utterly cruel. By the end of the story,
Ralph is being hunted by Jack and his hunters. Ralph and his representation of good
versus evil is losing the battle. If the naval officer had not arrived when he did,
Ralph very well may have killed by Jack and his cruel hunters.