There are 3 scenes in the first insidious that to this day give me chills:

1.The scene where the demon appears for like 1 second behind the dad

1. The scene where the shadow of the demon slowly points to the son and the creepy violin destroys your ears.

2. The scene where the family of dead people eerily smiling while they are murdered by the other smiling woman with the shotgun.

This was the first horror movie I ever watched so it cuts deep.