Cyberdemon

The cyberdemon is usually seen as the most powerful enemy you encounter in doom. His first appearance was in Ultimate DOOM the the last stage of episode 2 in Tower Of Babel.

The cyberdemon has goat legs but one of them is metallic or perhaps robotic. His weapon is a rocket launcher that replace one of his hand. His tactic is to mindlessly shoot 3 rockets in a row at the player which deals tremendously high damages even at the lowest difficulty. However this is his weakness because a player with some experience will be able to dodge the rockets easily because of the simple attack pattern it uses.

In DOOM II, in the stage named GOTCHA!, this stage is meant to show a battle between a cyberdemon and the final boss of Ultimate DOOM, the spider mastermind. The cyberdemon usually always win unless the player interfer.

The cyberdemon makes a come-back in DOOM III where he is the final boss of the game. Despise his incredible damage rating, if the player defeats it the usual way, the cyberdemon is quite easy to vanquish.

The most powerful enemy in the Doom series, also a signature. The Cyberdemon is an enormous bull-headed demon with mechanical add-ons such as a torso with wires, a metallic foot, and above all, a big fat rocket-launcher.

The Cyberdemon makes a return in Doom III, but apparently plays a very significant role in the game (no, you don't play as him, but he has a major purpose in the storyline). Also the Cyberdemon looks bigger & badder than his predecessors.

20 feet half robot-half demon that shoots rockets from the DOOM video game series. It doesn't take any splash damage, and most probably the strongest enemy in the game. First appears in the last level of the second episode from the first game as a boss, but becomes a regular enemy in later levels and games.