Former Commando (Chaingunner)
"Geeze, weren't shotgun zombies bad enough? At least when you fade these jerks you get a cool chaingun." (Doom Wiki)
Fast firing hit scan attacks that will melt your HP down from a far distance, these undead menaces should almost always be the top priority target in any fight.
Former Commando CREATURE 3
chain gun +14 (agile, range increment 120 feet, reload 0) 1d6+5 piercing
The former commando makes three chain gun attacks. Apply its multi attack penalty to each Strike normally.
Hell Knight
"Tough as a dump truck and nearly as big, these Goliaths are the worst things on two legs since Tyrannosaurus rex" (Doom wiki)
These towering brutes are basically just a recolored Baron of Hell but with slightly lower stats (except for health which got a huge drop)
Hell Knight CREATURE 4
claw +122d10+7 bludgeoning plasma ball +14 (range increment 60 feet, reload 0)2d8+5 fire
The hell knight makes a melee Strike. This counts as two attacks when calculating the hell knight's multiple attack penalty. If this Strike hits, the hell knight deals an extra die of weapon damage.
Spiderdemon
"You guess the Arachnotrons had to come from somewhere. Hi, mom. She doesn't have a plasma gun, so thank heaven for small favors. Instead, she has a super-chaingun. Crap." (Doom Wiki)
Imagine if you took the chaingunner and then turned them into a giant spider and vastly increased the health. Now you have the spiderdemon, have fun trying to kill this thing!
Spiderdemon CREATURE 7
chain gun +20 (agile, range increment 120 feet, reload 0) 2d6+6 piercing When the spiderdemon is destroyed, its mechanical torso explodes as the demonic energy holding it together is released. Adjacent creatures take 4d6 fire damage with a DC 23 basic Reflex save.
Revenant
"Apparently when a demon dies, they pick him up, dust him off, wire him some combat gear, and send him back into battle. No rest for the wicked, eh? You wish your missiles did what his can do." (Doom wiki/Doom II Manual)
These skeletal demons can rain hell down on your with their homing missils, chasing you all around the battlefield until it finally hits and deletes half of your health. Don't think that getting in close will solve your problems however, because it has a nastly punch attack as a backup.
Revenant CREATURE 5
punch +13 2d8+7 bludgeoning homing missile +15 (range increment 60 feet, reload 1) 2d8+7 fire plus 2 splash piercing missile +11 (deadly d8, range increment 60 feet, reload 1) 2d12+7 fire plus 2 splash piercing The revenant Strides, Steps, or Sneaks, then Interacts to reload.
Mancubus
"The Mancubus is a horrendously large, cybernetic humanoid monster shambling about on sturdy, stumpy elephant-like legs, glaring at opponents through hateful green eyeballs without irises or pupils, while dribbling the remains of dead victims from its lusting mouth, displaying sharp yellow fangs. To make matters worse, it has huge flamethrowers for arms" (Doom wiki)
These brutes can fire a surprisingly large amount of fireballs at you in their volleys, and they can sustain a lot of damage before they go down.
Mancubus CREATURE 5
flamethrower +11 (twin, agile, range increment 60 feet, reload 0) 2d8+7 fire The mancubus makes three flamethrower attacks. Apply its multi attack penalty to each Strike normally.
Arachnotron
"Maybe cybernetics wasn't such a great idea after all. Look what the demons have done with it. It seems unfair somehow you're not the only guy in Hell with a plasma gun." (Doom II Instruction Manual)
They look like smaller spiderdemons, but they have a plasma gun instead of a chaingun, which at the very least is easier to dodge than the spiderdemon's hitscan attacks.
Arachnotron CREATURE 3
plasma gun +12 (agile, reload 0, range increment 60ft)1d10+6 fire When the arachnotron is destroyed, its mechanical torso explodes as the demonic energy holding it together is released. Adjacent creatures take 2d6 fire damage with a DC 18 basic Reflex save.
Pain Elemental
"What a name. And what a guy. Killing him is almost as bad as letting him live." (Doom II Instruction Manual)
This things are one of the most annoying enemies in the game. They spawn legions of lost souls to charge you down, and even when you finally take them out they spawn a handful of new lost souls as they explode.
Pain Elemental CREATURE 5
jaws +132d6+6 piercing (Flourish) The pain elemental summons one lost soul on a tile within 10 feet of it. Place its initiative immediately after the pain elemental. When the pain elemental is destroyed, it's body explodes and it spawns 1d4 lost souls spread out on tiles within 10 feet of the body. Place their initiatives immediately after the pain elemental.
Lost Soul
"The Lost Soul is a flaming, flying skull with two horns, orange eyes with yellow dots for pupils, and very sharp teeth." (Doom Wiki)
These demons just fly right at you and start biting you until you kill them, or they kill you. That's it. The only good new is that they have low health.
Lost Soul CREATURE 1
jaws +121d6+3 piercing The lost soul Flies twice. If the lost soul ends it's movement within melee reach of at least one enemy, it can make a melee Strike against that enemy.
Archvile
"One of the worst of a bad lot. You can't think of enough rotten things to say about him. He's fast, hard to kill, casts spells, and resurrects dead monsters! At least these suckers are rare." (Doom II Instruction Manual)
The deadliest enemy in DOOM II, Archvile's speedily sprint across the battlefield, shooting fire at you for almost all of your health, and if you have the audacity to kill anything other than it, it'll just bring them back and now you've gotta kill the demons all over again. The only good news here is that they can't resurrect other archviles, else they would be even worse to fight.
Archvile CREATURE 7
fire +20 (reload 0, range increment 60ft)2d8+8 fire The archvile shoots fire in a 60-foot line that deals 8d6 fire damage (DC 23 basic Reflex Save). The archvile can't use Immolate again for 1d4 rounds.
The archvile targets one dead ally's body within 10 feet who has died within the last minute. The target must be level 5 or lower. The target returns to life with full hit points and the same spells and points in their pools they had when they died. 
All art and original monster ideas from the ID Software team and from DOOM (1993) and DOOM II, I'm just making pathfinder 2e statblocks for them.