Scary monsters

Scary movie monsters has existed since the birth of the tv and the silver screen. But what is the most terrifying of them all?

Since I was little ive allways thought of the movie IT to be scary and well shure it probably is when your eight years old. But since then I´ve been introduced to more and more (in their own ways) scary creatures.

For me I still love the aliens from the Alien quadrology, they seem to have it all. Speed, strenght, endurance and brutality.

What´s yours?