The boss is going to be big, abnormally big, but not huge. It is like the tank from L4D, but not only does it use a weapon and stand on it's legs, it is very slow due to it's size, But the area you will be fighting in is going to be a big cage-like area, so you can't run away, and there is little to help you.
However, if it gets you, it will be a one hit kill, as it can spear you in different actions with animations.
The face is torn away as well as the eyes and the jaw, which resembles a loss of identity, and that it is no longer a human, and the fact that there is a lot of blood on it and it is completely disfigured would make it more terrifying to the player in low light resolutions.
Unfortunate this will have to wait until I can find someone good enough and willing enough to create this boss, as I do not posses the equipment to do it myself.