I did say I’d be posting some really dumb ideas didn’t I?
Just about every member of the animal kingdom has been featured as the KILLER in some story or other. The Birds. Frogs. Grizzly (to pick one). Willard (and his rats). Worms (Squirm). Slugs. Crabs. Piranha. All sorts of killer bees in movies and books. Lots of killer spiders.