A really good monster, in my mind, has one trait taken to ridiculous heights. Jason Voorhees (from Friday the 13th
) is unstoppable, as are Bruce the shark (from Jaws
), the Mummy, and any Bond villain's henchman (such as Oddjob). A vampire is like someone who comes to you for support—moral, financial, or whatever—and won't let go. A werewolf is like the guy who goes to a party, trashes the place, and doesn't remember it next morning. And so on.
The trait can also be a belief. The monster may believe in or want something so badly that she will kill for it.
If the monster is (or appears to be) human, there's typically one inhuman feature: fangs, a mask, a concealed weapon, etc.
Under World. It rocks!