i was building a monster for my camping and I was thinking that maybe I should that creature something that causes deafness and it benefits from it in order to kill but being deaf doesn't seem as big of a deal as much as veing blind or paralized. Is there a way to make it dangerous?  

You could place the monster in an environment where they're are many unseen hazards that could be triggered in lair actions - the hazards could have an audible early warning sign which is negated by the creature being near by. For example, some kind of gas spore that gives off a whining noise 1 round before it is going to trigger... If the players could hear it, they'd have a chance to move out of the radius of the hazardous gas before it poured out.

You could also make it so the creature has spines that give off an aura of silence, as a lair/legendary action it can fire them out around the environment causing spell casters that need vocal components to have to constantly move around. 

Create an area with lots of cover and dim light / shadows and use enemies that use skirmish tactics while sneaking around, or that use invisibility.

Give the deaf characters disadvantage on perception rolls, because they have to rely on visual clues only.

And when deaf, let them fail any attack on invisible enemies.

Make sure to mention to them at least a couple of times how eerie the PCs find the absolute silence of the encounter. Point out how they can see heavy things fall, feel the vibrations of the impact through their feet, feel the displaced air flow across their faces and bits of debris hit their legs...

but hear absolutely nothing.

You can also create a scenario where they shouldn't trust their eyes. High-level illusions. Hallucinatory terrain. Delusions or mild insanity. Maybe there's a disembodied voice they need to follow to escape a dungeon or locate a magical object, and if they don't hear it, they could wander into something awful.