I saw this when I was 9 or 10
Belial was one of the most craziest, disturbed characters I had seen in a horror movie at the time. The fact that something (or in this case, someone) that tiny could wreak so much havoc and leave people dead with zero chance of survival was a scary thought. The fact that you can't even reason with him, and the one person who could call off the attack simply won't, was very unsettling.
After it was over, and trying to sleep, I kept being bothered by one thought: HE IS SO SMALL HE COULD BE IN A BOX IN MY ROOM! HE'S PROBABLY IN HERE WATCHING ME!
I'm so scared your little head will come off in my hands!