Demon/Doom 3

The Demon in Doom 3 (a.k.a. Pinky) is very much different from its older versions. It has no visible nose or eyes, walks on all fours, has a more animal-like appearance, and has cybernetic rear legs.

Trivia

 * In the Doom movie, the character Pinky turns into a Demon later in the film. This is evident, as the monster inherits his bionic-wheelchair contraption.