Cyberdemon

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. Fortunately, there are plenty of lesser demons on the level that can be killed to charge the Soul Cube.