HP: 20
Damage: 3-15 (Bullet)
Pain Chance: 78.13%

This guy is essentially a zombified human with a gun. He's more of an annoyance than an actual threat, being armed with merely a single shot rifle. Drops a clip when killed. Along the other zombies the only enemies that drop ammo for you in the game. When fighting other monsters, this guy doesn't stand a chance against anyone but his own kind.

Countermeasures: Pistol or better.

Danger Level: 1

Not very threatening. Dies to everything and keels over easily. Unless you are at less than 10 health with no armor, you needn't fear these guys.

HP: 30
Damage: 9-45 (Shotgun Blast)
Pain Chance: 66.41%

This guy is much nastier than is brown counterpart. He carries a shotgun which can be quite a pain at close range. Once killed, he will drop it so you can pick it up. These guys can be really dangerous in groups so try to make them shoot each other. In case of infighting, I have seen these guys kill enemies up to a Pinky Demon.

Countermeasures: Shotgun or better. Chaingun is particularly effective.

Danger Level: 3

Lone shotgunners are an annoyance, a group can be devastating. Use cover and peek-a-boo to take them out a bit more safely.

HP: 60
Damage: 3-24 (Claw), 3-24 (Fireball)
Pain Chance: 78.13%

One of, if not the most common demon creature. This guy can be annoying and only gets really dangerous in big groups. The danger in that lies in the fact, that unlike zombies, these guys are impervious to their own fireballs. The fireballs themselves are easily avoided, but narrow corridors can become a pain. It's claws hurt just as much, so don't get close to this guy for too long. When fighting other monsters, he can take out zombies and sometimes Demons.

Countermeasures: Pistol when encountered alone, shotgun or chaingun for groups.

Trivia: It's death sounds are apparently recorded sounds of a camel.

Danger Level: 2

The most vanilla enemy ever, but that doesn't mean they are harmless. Their melee attack is quick, so try not to get surrounded!

HP: 150
Damage: 4-40 (Bite)
Pain Chance: 70.31%

This creature may look like the pink version of Zuul but there's nothing amusing about it when it bites your arms off. They move fast to make up for their lack of a ranged attack. "Pinky" can bite his way through zombies and imps without much effort most of the time, should they get shot in the back by other monsters which happens quite often.

Countermeasures: The Chainsaw and Shotgun are your best friends but a chaingun works well too.

Danger Level: 1-4

Their danger level is solely depending on the map design and how many are coming at you at once. Open spaces? You can evade them all day long. Cramped corridors? That's when they get dangerous. Try to keep as much space between you and them as possible. They are extremely deadly on Nightmare!, which is where I'd rate them a 4.

HP: 150
Damage: 4-40 (Bite)
Pain Chance: 70.31%

This guy is essentially the same as a Pinky demon. However this one has partial invisibility (hence no pic) by default. Otherwise the same deal, just be cautious in dark areas if you hear a Pinky's roar. These guys can sneak up on you fast and get easy bites in.

Countermeasures: Same as Pinky.

Danger Level: 2-4*

Just like with the Pinky, the map design matters where open spaces are no problem and close quarters can be very tense. Except here, dark areas can hide these guys well if you are using the original software blur effect, so spotting them is a little trickier sometimes. They are also deadly turbo monsters on the Nightmare! setting.

HP: 100
Damage: 3-24 (Charge)
Pain Chance: 100%

By far the most annoying creature in all of Doom history. Lost Souls usually come in numbers and are not as easily killed as one might think, taking 2-3 shotgun blows to die. Their attack doesn't hurt much, but they can charge you in rapid successions, especially in a group. They aren't that useful for making them fight other monsters, as they "forget" their target after hitting it once. However you can still make them ram each other over and over despite.

Countermeasures: Chainsaw (close quarters),Chaingun, Shotgun and Plasma Gun.

Trivia: This is the only monster in the original Doom with a 100% pain chance.

WARNING: Using a rocket launcher isn't smart, as tempting as it might be to shoot one into a swarm of these things. If the Lost Soul you target starts darting towards you, you could not only end up frying it, but yourself as well...

Danger Level: 1-2

As long as you can intercept them before their charge connects, any gun can stop them. They are only really dangerous in levels with tons of them.

HP: 400
Damage: 10-60 (Bite), 5-40 (Lightning Ball)
Pain Chance: 50%

This guy's grin is deceiving. This oversized beach ball shoots lighting balls that will hurt like hell. They float around and can be pushed away with sufficient force (think rockets or continous shotgun fire). Although it should happen rarely, getting bitten by one is certainly not recommended. When fighting other monsters, these guys can beat any low level monster and distract even the larger ones for a while.

Countermeasures: Shotgun (if ammo is plentiful) Chaingun (keeps them from firing), Rocket Launcher.

Trivia: Appears in "Wolfenstein: The Old Blood" as a hidden plushy easteregg. It's also this author's favorite Doom monster.

Danger Level: 3

They are just tough enough to the point that you can't just breeze through them and they hit just hard enough to be considered dangerous. Plus, they can reach you almost anywhere.

HP: 1000
Damage: 10-80 (Claw), 8-64 (Energy Blast)
Pain Chance: 19.53%

This one you will meet twice for the first time. Two of these creatures will be the bosses of the first episode "Knee-Deep in The Dead". In the following episodes they show up occasionally as very strong enemies to fight. When fighting this thing, use strafing whenever possible. With 1000 HP, killing this dump truck can take a while. The powerful attacks he employs can easily kill you if you are injured beforehand. When fighting other monsters, the Baron pretty much always wins unless its fighting something bigger than himself.

Countermeasures: Rocket Launcher, Plasma Gun or BFG 9000.

Danger Level: 3-4

In open spaces where you have room to dodge, they are not that dangerous, but in close quarters they can end you quick. Let that help you decide your targeting priority.

HP: 3000
Damage: 9-45 (Bullet)
Pain Chance: 15.63%

The Spider Mastermind is the final boss of Doom. Although it has less HP than the Cyberdemon, it can be more dangerous to you. Unlike the Cyberdemon's rockets, the Mastermind's gatling gun is much harder to avoid and can hit you even at extreme range. Standing still is the worst thing to do, as he (it?) will turn you to shreds in no time. When fighting monsters, this thing mows down anything without much effort safe for Cyberdemons. Use cover and run whenever you can.

Countermeasures: Rocket Launcher*, Plasma Gun, BFG 9000.

Danger Level: 3-4

Yeah, a boss monster with a varied danger level. Here's why: In open spaces with no cover, you will die very, very quickly to this thing. But any walls guarantee your safety. Plus, this thing is so huge, getting it to infight is super easy which allows you time to line up that perfect BFG shot.

*It should be mentioned that this monster is immune to the damage from blasts. So only direct rocket hits will affect this monster and it won't do as much damage as a direct impact on a lesser monster.

HP: 4000
Damage:
20-160 (direct hit)
0-128 (blast radius)
148-288 (direct hit + blast radius)
Pain Chance: 7.81%

This is arguably the most notorious monster in the Doom series. He shows up first as the boss of the second episode "The Shores of Hell" and can also be found in a secret level in episode 3. The Cyberdemon can kill you in just one shot unless you have really high HP. The trick is to keep strafing and observe his attack pattern. He will walk for a bit, fire 3 rockets in a row and repeats. He only stands still when under massive fire (he gets stunned by the random pain chance) or when firing. Should you make this guy fight other monsters, chances are he will survive with little to no HP loss unless it is up against a Spider Mastermind or horde of lesser enemies.

Countermeasures: Rocket Launcher*, Plasma Gun and BFG 9000.

Danger Level: 4-5

Basically everything said about the Baron applies here, except that Cybie has 4x the HP and a much harder hitting attack. Give yourself distance to dodge and just plasma this thing away or swerve up close to BFG its face.

*It should be mentioned that this monster is immune to the damage from blasts. So only direct rocket hits will affect this monster and it won't do as much damage as a direct impact on a lesser monster.