Creepiest Movie Children - Rotten Tomatoes
The Good Son (1993)

Henry Evans is an enthusiast of typical middle school pursuits. Killing animals with crossbows. Dumping dummies in the way of motorists. Murdering siblings. So it's too bad his cousin Mark is such a square, narcing every time Henry tries to have a little fun. Given that Henry's parents are the least attentive guardians in cinema history, it's likely this little child psychopath's reign of terror would have continued unimpeded through grad school if it weren't for Mark.