Extra limbs?
Like four slightly over sized arms?
I just have a thing for arachnids and insects.
Hmmm four big arms and tiny legs dangling?
Or how about 6 arms total with 2 legs...but the arms are a bit longer and not big, this would give you your desired creepy man-spider look and function...even creepier if they were not all the same length, like a set of smaller ones close to the neck or midsection or asymmetrical with each being a different length...yikes!
Like the above except keep in mind...really ugly, not even remotely close to normal looks, each is their own version of a horror story...a face that is well hideous...weird warty/tumorous looking skin, etc.