Here are two examples of people who are not fully human. One never had full humanity. The other had lost it.
A boss I had about 35 years ago had the personality of a wall. But it was a wall made of concrete blocks or drywall and not from, say, bricks. They have some character with the mortar sticking out irregularly between them.
There was the mub: Half man and half grub. I once knew a man like that. He was pale with a very light yellowish tinge to his skin. He was bald and short: No taller than 5ft6in, if that. He also wore those eyeglasses where the lenses turn dark in sunlight; his glasses were like that when he was inside.
What was most creepy was that he spoke in low tones, as if he was selling drugs and pornography. And not, say, marijuana and Sports Illustrated/Playboy pinups; it was more like heroin and pictures of teenagers fucking.
These are from notes I found in my put-this-in-the-blog-folder. I decided to combine them because they are somewhat related.