What are the most frightening aspects of Lord of the Flies?

I think the most frightening aspect is the boys themselves. They so easily gravitate to disorder and chaos. Instead of respect they opt for subjugation by Jack. They kill Simon, their Christ-figure, and lay waste to the entire island. Golding puts man's essential nature on display and sums it up with Simon reflecting on the nature of the beast, 

However Simon thought of the beast, there rose before his inward sight the picture of a human at once heroic and sick.