Retarded Boy at River

No, the disabled guy was 'innocent' in that he had a naive, innocent evil, to just want the necklace. Thus he didn't enter in the revenge cycle.

[SPOILERS]
The people who were trying to get revenge were projecting their own guilt. They were unable to accept the guilt at what they had done.

Ryu was unable to accept that his sister killed herself because of him. The suicide note says that it is because he kidnapped the girl and lost his job because of her. She never would have wanted that, so she killed herself. He can't accept the guilt so he creates a revenge-fantasy-delusion and kills the organ dealers, but that still doesn't satisfy his illusion, so he eats their organs, becoming inhuman in his 'retribution' logic (eye for an eye, kidney for a kidney).

Park (the father) is unable to accept the death of his daughter, and when she appears to him as an apparition, she actually blames him for not giving her swimming lessons. In actuality, it was an accident, but he is unable to grieve (as seen in the cremation scene) and becomes hardened to autopsies. In the first autopsy scene he is frightened and sickened but in the second one he is cold, and by the end of the film, he has performed his own autopsy-butchering of Ryu.

In this way, neither character is able to deal with their guilty consciences so they externalize and project them through revenge fantasies.

How the disabled guy by the river ties into this to me is a few ways: the indifference of life, our inability to take action when confronted with existential dread, and also perhaps a naive or innocent evil which contrasts the evil perpetrated by both Ryu and Park in their quests for vengeance.

It is because of the disabled guy that the girl drowns (she is trying to avoid him after he was trying to steal her necklace from the car). And the disabled guy is obviously self centered and only interested in the necklace. But is he not a natural product of society, an innocently evil person who doesn't know any better? He is following the same drive for a shiny object that the innocent girl had when she accepted the necklace in trade for her doll.

My take on it: Both Ryu and Park are driven by their corrupt, dark, "evil" revenge drives, and thus they enter into the revenge cycle and are punished for it. But the disabled man is not punished because he is does not understand ilfe and death, or right and wrong. He is basically innocent by factor of his disability (even though the cops say he is not stupid, and of course, many people with CP are highly intelligent). But I do believe that he has a sort of inability to understand life and death, in that he doesn't even try to save the girl from drowning. And thus he is not punished-- he does not enter into the revenge cycle.

... he probably has Muscular dystrophy (MD), and is NOT retarded (i.e. downs syndrome, etc.) He can't walk and talk very easily, but his cognitive ability is not very diminished (if at all);

Well even when the girl was dead all he cared about was getting the necklace, there must be something wrong with him mentally.