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, its horns point straight forward instead of out from the side of its head, walks on all fours, has a more dog-like reptilian appearance and has cybernetic rear legs. When it is summoned, it makes a screen-shaking effect when it roars.

It attacks in a similar fashion to its classic version by running up to the player and biting them, but due to the player's reduced movement speed, it is much harder to escape from and due to an increased attack speed and range, the attack is much harder to dodge. Additionally, being hit by an enraged Demon disrupts the player's aim, which is very confusing and makes a counterattack nearly impossible.

Like the Doom 3 version of the Imp, the Demon is tougher than its classic counterpart due to increased firepower in some of the weapons, but it still takes only around two shotgun blasts at point-blank range to kill it.

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. Why he didn't just mutate into a wheelchair equipped zombie is unanswered. One explanation is that because there is technically "less of him" than normal humans, the mutation was more concentrated.
 * The designers have explained the unique face of the pinky demon by describing how it is born: a newborn Pinky's face is buried under thick folds of flesh (that do not, unlike other animals, undergo apoptosis), and the animal must consume itself to breathe and eat.
 * It should be noted in some places in the Hell level of Doom 3, the organic half of this demon can be found hanging on meat hooks. Why they are there is unknown, but they could be used as a food source.