Buhguul's clothes
I just realized one gripe I have about the way the filmmakers decided to dress Buhguul. The first few glimpses of him as just a face hiding behind the bushes and then all distorted underwater in the pool, absolutely terrified me.
But then I found him less scary when I saw that he's wearing some kind of black suit and a white dress shirt like he just finished a rough day down at the accounting office, lol. For some reason, I don't find monsters dressed in business attire to be scary. It's the same reason Slender Man does nothing for me in terms of fear.
When you first see Buhguul underwater, probably because of the distortion of the water, it looks like he's wearing a long black robe. I think if they ran with that, instead, it would have given him a more ancient and otherworldly vibe.