gaudi said
What Brovo said sums it up.
Honestly, the hardest ones I can think of are the ones that hit your sensory inputs. That is: Seeing, touching, smelling, hearing, and tasting. There's also varying degrees of "difficulty" that can be most easily discerned with sensory input deprivation. For instance: Someone who is colour blind merely can't see colours, everything is a shade of grey. It's interesting to write and not too difficult: When someone describes the colour "blue" to you, you don't see blue, you see another shade of grey. The next difficulty step is sight damage of some sort, such as near sightedness that turns everything beyond an arm's length away from you into a blurry mess of indistinguishable blobs, it usually makes you dependent on glasses or other such ornaments in order to see properly.
Finally, you have total blindness. This is basically flicking the switch from "hard" to "borderline impossible" for most stories, though especially action-oriented tales. Everything that has a visible descriptor no longer functions as a description for a blind person. After all, a blind person cannot visually comprehend
anything--how bright something is, colours, texture unless they can touch it, and so on. This is made even
harder if the character was born blind, because then, well, they literally have no memories of sights at all to pull from, and so when someone says that something is a big blue ball, they have utterly no frame of reference for what that is beyond the feeling of a ball in their hands.
Since everything in writing is some form of description, to take away a sensory input is to deprive the writer of a significant portion of their ability to produce descriptions. Imagine trying to describe how something looks without being able to use the visible spectrum at all and that's blindness. Both Gat and I learned the hard way that while intriguing it was often more trouble than it was worth.