In the arena of human/animal combinations — no one beats the mythology of ancient Egypt. These were gods, not monsters, but these human/animal mash-ups turn out to be wonderfully monstrous.
Anubis, as the god in charge of embalming the dead, holds a very special place in civilization that was focused on the afterlife. With a jackal’s head and a man’s body, Anubis is pretty scary.
Bastet is the ultimate cat lady. No, she did not live in a small house with 50 cats; she had the head of a cat on a woman’s body. She was a protective goddess, but, like a mother cat, she could be fierce too.
With a hawk’s head on a human body, Horus would definitely fit the bill as a nightmare monster. The son of Isis and Osiris, he was the god of the sky. Horus was the protector of the pharaohs and they were, in turn, considered to be the living embodiment of Horus on earth.
Ra also had a hawk’s head on a human body. The god of the sun, he was the most important of all the Egyptian gods. But his ID was more complicated. Each night Ra was said to be swallowed by the goddess of the sky, Nut, and reborn each morning with the sunrise. During his nights in the underworld he had the head of a Ram. Obviously, he couldn’t be careless about where he left his head. (Yes, I made that joke. It was just too hard to resist.)
The goddess Tawaret is still the best of the Egyptian monster mash-ups. She was the goddess who protected women during pregnancy and childbirth. With the head of a hippopotamus, limbs of a lion, tail of a crocodile and the torso of a pregnant woman — she was quite a sight. Very confusing!
There are three more that I just have to mention: Sobek, the god of the Nile with a crocodile’s head; and Sekhmet, the goddess of war, with the head of lioness. Set (AKA Seth) was the god of chaos, storms, winds and other dark and evil things. What was his monster mash-up? A chaotic assortment, sometimes he had the head of a jackal, sometimes a crocodile or a pig or hippopotamus — he was the god of Chaos, after all. He is the best monster of the bunch.