Shelob because unlike Pennywise, She doesn’t have to dress up like a clown and instead appears as her genuine and honest design self

"Hardly had Sam hidden the light of the star-glass when she came. A little way ahead and to his left he saw suddenly, issuing from a black hole of shadow under the cliff, the most loathly shape that he had ever beheld, horrible beyond the horror of an evil dream. Most like a spider she was, but huger than the great hunting beasts, and more terrible than they because of the evil purpose in her remorseless eyes. Those same eyes that he had thought daunted and defeated, there they were lit with a fell light again, clustering in her out-thrust head. Great horns she had, and behind her short stalk-like neck was her huge swollen body, a vast bloated bag, swaying and sagging between her legs; its great bulk was black, blotched with livid marks, but the belly underneath was pale and luminous and gave forth a stench. Her legs were bent, with great knobbed joints high above her back, and hairs that stuck out like steel spines, and at each leg’s end there was a claw."

— The Lord of the Rings: The Two Towers