Former Human Commando
This guy is as mean as he looks! That chaingun of his can chew up some serious ammunition from near and from far. You will usually find yourself flanked by these bad boys and in a position where by the time you realize what happened, you are already dead. The up side to this is that when they die, they are kind enough to leave you a chaingun and ammo to use in future battles. Lucky you, cuz you're gonna need it! A couple of shotgun blasts will usually take this badass out but don't just stand there firing or you'll discover that the casket doesn't open when you're underground. Stand behind a corner or some other obstruction and take potshots at this guy till you've taken him out. If you MUST stand toe to toe with him, use the best weapon you have and use it FAST!
 

Imps
These can be a nasty lot if you encounter them in large numbers or unexpectedly. Up close, they can rip you to shreds with their claws but from a distance a well placed shotgun blast is the way to go. Usually, if they are only a few feet away, a single shotgun blast will do the trick from the regular shotgun. From a longer distance the double shotgun is just as effective. If you find yourself up close and personal with these guys or are in a roomful of them simply keep moving and firing rounds at them. They aren't very fast and the fireballs they chuck aren't either. Just don't forget to keep moving. Up close they can be fairly dangerous. At a distance it's like picking off skeet that are moving in slow-mo.
 

Demons
These guys are BIG, slow, and pink. They will also chew you a new one in a hurry if you get in front of them. A double barrel will usually dispense with them in one quick shot but the chainsaw is a hell of a lot more fun and saves ammo too! Don't take these guys lightly though, they can mess you up REAL FAST!
 

Specter
You may be wondering why you're looking at an empty picture frame. It's because these bad boys are INVISIBLE! I hate running into these guys in dark alleys because they are impossible to see. In the daylight you get a little inkling of them but in the dark, you are screwed! That's what they make save slots for, so use them!
 

Lost Souls
These little bastards are fast and furious but for all that thunder (and screeching), they aren't very dangerous. Just don't let yourself get surrounded by a bunch of these little where they can take their time to do the lost soul shuffle on you by taking some bites out of your ass and burning you to a crispy marine flambe'. A couple of well placed shotgun blasts or some bursts off of the chaingun will wreck these guys night real fast.
 

Cacodemons
Don't let these guys fool you. They might be big and they might be ugly but they are dangerous, especially in close quarters. From a distance they will shoot blue fireballs at you and fry your ass. Up close an personal they will eat your head off and drink the blood as it squirts from your decapited body! They aren't usually a big problem as long as you have a chaingun handy. A few well placed shotgun blasts will also do some major damage to them as well. Just don't make the mistake of ignoring them if there are other badasses to battle!
 

Hell Knight
Knighted by Satan, himself, these bad boys can lay down an ass-whuppin! Don't get too close and use your shotgun while strafing from a safe hiding spot to get rid of this guy. If you get in the way of his attack you are done for!
 

Baron of Hell
The Baron of Hell is a VERY tough customer and somebody you DON'T want to get to know up close and personal, if you can avoid it. He shoots fireballs that look like plasma shots and each hit is quite capable of turning you into worm food. Strafe and keep on strafing and if you can, hit this guy with your plasma gun, BFG, or chaingun. He will eat up alot of rounds before going down so use the biggest weapon you have. If you're using the rocket launcher, don't forget to hit from a distance or you'll end up toasting yourself as well. Whatever you do, though, DON'T stand still or your boots might be the only thing left standing!
 

Arachnotron
These are like baby spiders (as compared to their much larger and more dangerous bretheren, the Spider Mastermind. Don't take them lightly though and hope that you get caught in their sights from a distance! They shoot plasma as fast as your plasma gun and it won't take but a couple seconds of that to turn you into Batha fodder! The chaingun, or the rocket launcher is usually your best bet with these little sons of bitches! Don't stand toe to toe though, you WILL lose.
 

Mancubus
He's big, he's fat, he'll kick your ass! This big boy has two giant guns on the end of his arms and if he sees you before you see him, you will be toast before you can say "Marshmallows!". Fortunately, his attacks are predictable and as long as you stay out of his line of fire and time your return attacks in between his, you will be fine! Plan on several double shotgun blasts, a couple or three rockets or a steady barrage from your plasma gun to lay this big boy to rest!
 

Revenant
This isn't someone you want to bump into, especially in close quarters. Up close he packs a hell of a punch, literally, and from short to long distances he has shoulder fired rockets which actually track you. The best method (I found) of dispatching Sir Revenant is to simply riddle him with bullets from your chaingun. Like many of the creatures in Doom2, the chaingun (as well as the plasma rifle) tend to prevent them from executing their attack while you blow them away. A couple of well placed shots from your double barrel will also do the trick but it may not be fast enough to stop him from wiping you out. His rockets can be avoided, as well, as long as you are fast. Strafing is the best method for doing this. Wait for the rocket to be right on top of you then take a quick step left or right and it will go right by you. Try to outrun it and you will be demon meat!
 

Pain Elemental
Eerily resembling the Cacodemon, who was introduced in Doom, the Pain Elemental poses a completely different problem and is much more dangerous than the Cacodemon. Not only do you have to contend with this big boy but he also has this nasty habit of spitting out Lost Souls! If you don't take him out pretty quick, you will find yourself being overwhelmed by Lost Souls and most likely eating dirt for eternity (or until you return to your save slot). Again, I refer you to your chaingun or your plasma gun (if you have one) to take care of this guy. Shotgun shots will do it but again, may not be fast enough to stop you from getting your ass kicked!
 

Arch Vile
Ok now we're starting to get into the REAL badasses of Doom2. The Archvile is fast and will turn you into a roasted marshmallow before you can say "Stay Puft". This guy winds up and tosses a fireball on you that will kill you in a heartbeat. Your only protection is to duck behind something and then pop out and blast him with the plasma gun or two or three well placed rockets. You can kill him with other, smaller weapons but don't count on having the time. Oh yea, one last thing, if you don't kill him quickly, he raises other creatures, that you just spent your hard time fragging, from the dead. Don't screw around with this guy. Take your first opportunity and blast his ass back to the bowels of Hell.
 

The Spider Mastermind
See the chaingun just under the spidey's face? Stay the hell out of the way! This bad boy not only can take a shitload of damage but if he zero's you, you are going to get chewed up into little tiny pieces. Fortunately, because of his size, he is somewhat slow and has trouble keeping up with fast moving targets - so move ass and fire on the fly! The plasma gun or the BFG is your best bet with this big boy!
 

THE Cyberdemon
Give this badass some respect! Look up the word "hardass" in the dictionary and you should find a photo of this guy right next to the definition. You won't see him often in Doom2 but when you do, be afraid, and get out of his sight! Not only can he take four direct blasts from the BFG before being toppled, but he also fires a very nasty rocket barrage at you which will kill you instantly on a direct hit. If you can, find a small area to snipe at him from and then take your shots! He fires a burst of three rockets, then takes a quick breather before firing on you again, so when he gives you the break, take your shot then get under cover again! Anyone who has played Doom or Doom2 will tell you that this guy is as vicious as they come and as deadly as a Viper.
 

The Player
You are mankind's last hope! You've entered the very bowels of hell with a pistol. A pistol? Holy shit, dude, smoke a fatty and start killing stuff and scoffing up the ammo and weapons they leave behind! Your buds are dead and are coming after YOU. So how do you fight these guys? What can a lone marine, trapped in Hell, do?

 First off, keep in mind the intel I've provided on the various creatures, above.

 Secondly, learn how to fire on the fly and even more importantly, since you MUST download a port like Zdoom or Legacy to play on an XP machine, learn how to strafe! Strafing is your best friend in Doom and Doom2! A quick step to the left or right when standing toe to toe with a Baron Of Hell is probably the only thing that will be standing between you and a hole in the ground.

 Keep in mind also that the creatures in Doom and Doom2 aren't too bright! They WILL fight each other if you can get the ruckus going. It's actually pretty cool to watch a Spider Mastermind and the Cyberdemon duke it out after you get it going by taking a couple shots at them and get them turned in the right direction. I think you know who will win that battle every time though, don't you? The best part of that, of course, is that the Spidey WILL weaken him for you. Still, avoid him if you can. As for the rest of them, let them duke it out amongst themselves if you can get them to do it. You can mop up the survivors afterwords and reap the rewards that they leave behind for you to pick up. Why waste your precious ammo on these guys if they'll do the work for you?

Speaking of conserving ammo - don't use weapons you don't need to kill something. Using a plasma rifle to kill an imp is simply a waste of ammo and will most likely cost you your life later in the game! Use your pistol when possible, or the chainsaw if you have it. That one works great on weaker enemies and conserves your ammo. Use the double barrel sparingly! It packs a wallop but it chews up ammo like there's no tomorrow as well and you don't want to be facing a Hellknight with a pistol and a chainsaw. You will most likely get your ass kicked in a New York minute. Well, that's it for now. You should be prepared to meet and greet some of these badasses on the playing field, so get your ruck, grab your weapon and start killing something soldier!