Cyberdemon/Doom 3

The Cyberdemon is the final boss and most powerful monster of Doom 3. It stands roughly 20 feet tall, more than 3 times as tall as a human soldier. Like its original counterpart, the Cyberdemon attacks by firing a salvo of 3 consecutive rockets from its arm-mounted rocket launcher. Unlike the original version, it can also step on the player, killing them instantly.

Unlike its original counterpart, it cannot be hurt with conventional firepower; instead, the player has to utilize the most powerful weapon in Doom 3, the Soul Cube, to kill it. The Soul Cube states that only it can kill "Hell's mightiest warrior" presumably referring to the Cyberdemon. It takes 4 shots from the Soul Cube to kill the Cyberdemon (possibly a reference to the 4 BFG shots needed to kill it in the Classic Doom series). Fortunately, there are plenty of lesser demons on the level that can be killed to charge the Soul Cube.

Some differences of this new incarnation of the monster compared to its classic counterpart can be seen on the picture to the right. Though it is not shown in the picture, this incarnation has a long tail, extending from the machinery on its back, and both legs are mechanical, as opposed to its original which only had one mechanical leg. Another noticeable difference is that the rocket-launcher is now located on the right arm instead of the left.

The Cyberdemon did not make an appearance in the expansion pack Resurrection of Evil, so the one that was killed at the end of Doom 3 was supposedly the only one.

The Cyberdemon is also the only monster from the original games to be a boss.

Trivia

 * The Cyberdemon can be found in the game files of the Doom 3 expansion, Resurrection of Evil, but when it is spawned (for example by using a cheat code), the Cyberdemon appears to be vulnerable to regular weapon fire.
 * The Cyberdemon is referred to as "Hell's mightiest warrior" by the Soul Cube. Although technically the Maledict is Hell's mightiest warrior as it has more health points, the Maledict is vulnerable to conventional weapons, unlike the Cyberdemon which can only be harmed by the Soul Cube. Furthermore, the Maledict hadn't actually been created when the Soul Cube said the above statement, so there was no error.
 * In the final cutscene of Doom 3, the Soul Cube cuts off one of the Cyberdemon's legs, the one opposite the rocket launcher. This may be a callback to Classic Doom games, where the Cyberdemon had one robotic arm and one robotic leg. However, as mentioned above, the arm and the leg are switched from the original (the cut-off leg is on the left instead of the right.) However, since the Soul Cube killed the Cyberdemon immediately after its leg becomes amputated, there was never a chance for its leg to be replaced by machinery. It should also be noted that both of the Cyberdemon's legs are robotic this time, instead of just one.
 * It is actually hilarious if the player spawns the cyberdemon while having the God Mode cheat on, as the melee and rockets will only bounce the player all over the place.
 * If spawned in some places, the cyberdemon will actually become stuck becuase it will have its body trapped in the ceiling. This is more annoying than funny, as the player will hardly be able to get past the cyberdemon without the noclip code activated.
 * It is actually possible to slay the cyberdemon before the end of the game. This happens when the players spawns the monster and uses the give all cheat to gain the soul cube, then after its first use, use the give ammo cheat to fully recharge the soul cube. However, this will not end the game.