I agree with you in that additional scenes in the end would have been nice like a pat on the back for Mark from both parents for how clueless they've been and for saving Susan's life.
The cliff ending I LOVED. Of course the mother chose to save the kid who tried to save her from her psycho killer son who tried to kill 80% of his family so of course that ending was satisfying. But I wanted more

The same as "Moby Dick" or "Great Expectations" - no point whatsoever.

For the person asking if he was Borneo or disturbed. Unless I am wrong I think the movie was implying that he was born with psychopathic tendencies. At least from what they showed the family did not seem to be dysfunctional and the parents and sister seemed very loving and understanding. As far as we know also Henry did not suffer from something like schizophrenia that could make him act bad. His little sister seemed like the type to want to try and love her brother even when he was not nice to her and the mother seemed very understanding and caring. Notice also in the playground scene Mark says something about what if something just is regarding Henry and his behavior and it not being connected to anything wrong around him. Mark says this in response to the doctor saying there is a reason for everything. But there appears to be no reason for Henry's bad behavior. I read on this board a few people saying the reason is because Henry was jealous of attention paid to other siblings. Nothing is implied in the movie that the parents neglected him which might make him act out. His jealousy it seems was irrational and selfish. I think Henry was just born with psychopathic tendencies
The scary clown doll is hiding under my bed.

The only point is to scare you. Patricide and matricide are common fears.

There is no way this story ends well.
Any rainbows would come across as insincerely saccharine.

The all seems to end the same as well. You never see anyone pondering the question. Is there just no good way to end these movies?

The point is as with many creepy kid movies. Was he born evil or disturbed?

The point? Never have kids.

Yeah, it's pretty bad, can't disagree with you. Just a way to capitalize on Mac's fame at the time.