I've gone back to pen drawings for now.  I want to work out more ideas before I get into color.

Fear of being tied up or bound: The fearful is flexible like a snake, able to bend in almost any direction.
He is equipped with various blades and claws, which are able to cut through many materials.

Fear of being bound: The feared wraps its prey in tentacles and consumes it slowly, using a proboscis to drain fluids.

 Fear of chins: The fearful at the top and the feared at the bottom.

I tried to rethink fear of the dark: the feared object.  I wanted it to have more of a connection with the fearful object, so here is my new design.  The predator is small, it has a phosphorescent appendage of its own that it uses to attract the fearful object.  It consumes the fearful's light-casting appendage and stabs out it's eyes, permanently blinding it.

Fear of hair: fearful top, feared bottom

 These don't have predator/prey counterparts, but here are some more (I was trying to be more spontaneous with the designs, but I don't think they work as well).
1. fear of meat (herbivore)
2. fear of sitting (it's a head with legs, so it can't physically sit)
3. fear of perfection (this is the feared object, and none of its structure is symmetrical)
4. fear of numbers (the only thing I could think of was having no identifiable body parts that could be counted)

Then just for fun I started combining phobias.
Fear of smiling......and snakes.

 

Fear of bats and geese: