This is an incredibly frustrating achievement, but if you do it right it will only get easier as you go along.
Here is a general overview of how to get this and retain your sanity:
*WARNING* SPOILERS HEREIN *WARNING*
*I talk about particular sections of the game in this guide in order to talk about how to survive them! If you haven't seen this whole game through to the end, please finish a playthrough on a lower difficulty before even considering Hardcore.*
AT THE START:
- You'll need the Plasma Cutter and the Force Gun ASAP. If you don't have the Collector's Edition Force Gun or a DLC Force Gun, I would seriously contemplate downloading a force gun to make your life easier as you don't get the Force Gun until pretty late in the game. Otherwise, try to make do with the PC and get the FG schematic from the locker in Chapter 7 right after you get off the Tripod elevator.
- Consider kicking up the Brightness setting a couple of notches to take the edge off some of the darker sections of the game. (Thanks to Robotic Aquatic for this tip).
- At the first power-node-locked room (this is at the start of Chapter 2), be sure to open it up. The schematic for Power Nodes is in there. You'll need that so you can spend excess credits on upgrades for your stuff. As a general rule for store visits: once you feel satisfied you have enough health and ammo, consider buying a power node from the store.
- In the early game, you should upgrade your Rig's health and put down some moderate upgrades on your Plasma Cutter and Force Gun. Take advantage of the sparse amount of enemies to use Telekinesis impalement techniques on the enemies so you can conserve ammo and credits, increasing the amount of upgrading you can do by mid-game.
My saves were structured around places where I knew there were one-hit kills or tentacle grabbing sequences that I could easily die at. They weren't at the most ambitious locations but they can get the job done. If you want to try to get further on any one of these, go ahead, I've included some suggestions along with my actual save locations.
For instance, you might prefer more saves in the endgame. On the other hand, if you've played your cards right, the endgame should be easy enough to make the saves a non-issue. My suggestions are geared towards getting you in a situation where, by the drill ride, you're set to just blast through straight to the end.
So my suggestions are based on doing this in very moderate chunks.
Near the start of Chapter 5. Before the Church section where you get grabbed by the Tripod and get attacked by the Pack. I saved before the Crypt, but you can save closer to the actual grab if you want to (i.e. at the save station where you move the hanging coffins out of the way, which is the last before the grab).
I had already died on the Train Brute part once and didn't want to have to deal with another tentacle grabbing instant kill.
At the disc switch, as many people have noted. As of this writing, they haven't patched out this trick. If you die after the disc switch, you'll start right before the solar array. This will hold true until you exit the single-player game or quit to the Dashboard, so you must save before you quit. This is a nice way to break up the more difficult middle portion of the hard core run.
Start of chapter 9, right after you reunite with Ellie and Stross in the mining room.
Frankly because I was so sick of doing the solar array. But also because the end of chapter 8 has that tricky zero-g trap navigation sequence (big bad government man turns on the rotor blades) where I didn't want to risk more one-hit kills.
End of chapter 11, right before the drill room. I don't believe there's a save station IN the drill room, so you should save at the store/bench area just before.
I didn't want to risk the drill ride, but in retrospect I could have been more ambitious because the drill ride was a piece of cake. If you had no trouble with the mining elevator you should be able to handle the drill ride (as long as you have health packs), so I'd say you have a good chance of saving your last save for the start of 13. If you were barely scraping through the mining elevator sequence right before this, then you might consider putting down a save here. Then again, if the mining elevator is trouble, you've got more serious problems on your hands, namely: WHY aren't you using the Force Gun?
SPECIFIC PLACES TO BE ON YOUR TOES:
- The Brute who grabs you after you are hanging upside down from the train at the end of Chapter 2. Have your plasma cutter loaded and ready to take his arm out fast. This is early on, but if you hate sitting through the opening sequence each time you fail as much as I do, you'll want to be ready for it.
- The Tripod elevator sequence in Chapter 7 before the Solar Array. If you've gotten a Force Gun, your life will be much easier. It knocks them right off the elevator. If you don't have the Force Gun, be sure to pick up the schematic for it from a locker right after you get off the elevator.
- End of Chapter 7 flying segment, after you reset the solar array. Just look up a video of this sequence and watch it before you do it so as to save yourself the embarrassment of smacking your face into the apartment block. Memorize what's coming up and where to fly.
- Mining elevator: Force gun it, you knock everyone off.
- Drill Ride: Force gun it, you knock everybody clean off the rails.
- Lasers in the Government Sector: If you have low health, you might not be able to run fast enough to avoid the lasers. All the more reason to stay stocked up with health packs from the Drill Ride on out.
- The Eye Machine: Follow this rule all the way down: if the reticule isn't blue, my finger is not on the A button. Not blue, finger off. Take it slow and you won't mess up.
- Last boss. If your Force Gun is significantly upgraded you can just hammer the trigger over and over again. Not only will it destroy the Pack, it will wear down Nicole's health. Don't worry so much about spinning around, focus on the pack in front of you and catching Nicole in the blast. If you take damage, heal.
As soon as the Marker's heart is exposed, switch to your Plasma Cutter and wail on it. This is the MOST IMPORTANT THING: when the Marker heart is done taking damage and it starts to close again, DO NOT RUN AROUND. Nicole might respawn right next to you and you will die instantly. This happened to me twice. Just sit tight, and wait to see where she spawns (usually a set distance in front of you).
My winning playthrough of the last boss, I think I barely took a step. Just Force Gun it, and then PC it.
- Anytime you see a Pregnant. Those swarm can really deplete your health. Deal with them carefully. Especially the one in Chapter 8 -- he's around a corner in a very tight room and a slasher spawns right behind you when you see him. Get your distance.
- Anytime you see an Exploder. If they land a hit on you, it's gonna be game over. Get your distance. When you hear their characteristic noise, instantly locate them and move away.
- And any section with ONE-HIT KILLS. You should know where most of these are from your initial playthrough(s). Lots of the Zero-G navigation sequences have these - spinning blades, fire rings, etc.
- Restricting yourself to two guns really helps you with upgrades, ammo, and credit collection. You will almost exclusively get ammo drops for those guns, and any other ammo you collect can be sold to help you upgrade.
-By the halfway mark, you should be attempting to get both your HP fully upgraded and your weapons' primary fire as upgraded as humanly possible. Every so often throw a point or two into Stasis, having a long Duration and a couple more Energy will help with Brute fights and with the Big Bad Regenerating Dude at the end.
-Somewhere around Chapter 8, the tides should start to turn in your favor and you should start having more credits than you know what to do with. Use it so that you always have health and ammo on hands. If you're feeling ambitious, buy some power nodes. But first priority is having ammo and health.
- In general, hang back (until the end). Let the enemies spawn, get your back to a wall (or run back into the previous room), and take them out from safety. This is important especially in Stalker sequences. In the last 3 chapters, this does not apply. Just stasis everything and run from Chapter 13 on, except for an initial room that you have to clear to be able to hack a console.
- From the drill ride on out, just stuff your inventory full of health packs and ammo. HEAL whenever you are hit. Don't risk getting in the red. Having the Advanced Suit helps you with inventory slots - you can find this suit in a power node locked room in Chapter 11.
- By the endgame (Ch. 12), you should be set. Force Gun will let you just barge your way through the last few chapters and then you just have to do the boss fight (see tips above). I saved kind of early, but the drill ride was an absolute cakewalk so I didn't mind doing it a few times until I got the hang of the last boss.
This is my first (and maybe only) solution for this site. Please be kind in your feedback. This is drawn entirely from my experience playing through Hardcore over the last three days. If it worked for me, it can work for you. I am not usually one for the hardest difficulty setting but since I'm a huge Dead Space fan I had to take on the challenge.