Clad master's guide here is great and helped me out. I completed the game & all achievements (except for Self Defense and 100 Times Too Many, for obvious reasons) in one playthrough, i.e. on Hard. I can tell you that it's frustrating, but not impossible to get this achievement on Hard. A few additional tips:
There are seven instant death scenarios in the game:
- If you still have a Kinect connected (Xbox One only), turn off the Kinect Movement/Noise detection. They are a neat touch to the immersive experience, but this increases your risks of getting noticed (and subsequently killed).
- You want to be as stealthy as possible and not look for a fight. There will be rare times where running will be easier than slowly getting around people, but practice your ninja skills.
- You can part-build devices (ie don't hit
at the end to complete the build) to remove components from your inventory. This will assist in having plenty of parts in your inventory to build when you're desperate.
- The Pipe Bomb if thrown too close to you can kill you. Make sure you have a clear path to throw it far away from you.
- It hasn't been mentioned explicitly here, but when you're hiding in a locker or under a table/bed and you have the motion tracker on, the Alien can hear you if it's close by. It took me a while to understand why the Alien kept finding me. The same goes for Synthetics.
- Speaking of lockers, make sure that your health is always at or near 100%: when you're in a locker and you're given instructions to hold your breath, eventually your health will start falling. Usually the Alien isn't around long enough for this to be a serious problem, but you'd hate to die through lack of oxygen.
- If you're not sure whether you've died or not, you can always check the progress against "100 Times Too Many" (Xbox One only). If you end up dying early on in the game and didn't realize (i.e. you thought you reloaded in time but didn't), you'd rather know you've already blown the achievement early on, right?
- In particularly tense parts where you're being hunted by the Alien or Synthetics, have your right thumb hovering over the
button. While usually you'll have a few seconds to hit it and load from a previous save, there are times where you're just going to want to remove all ambiguity and hit reload straight away. Luckily the Alien generally gives you warning (its scream) before it gets too close to you.
- I found that the Alien either got more used to being hit by the flamethrower later in the game, or it wasn't as effective. In other words, be prepared to needing to hit
more (but still in short bursts) than a few times to scare it off in later missions. Flamethrower fuel is somewhat scarce in Hard mode, but as long as you're not too trigger happy with it you will have more than enough, and the game does provide fuel in key parts of the game where it's basically impossible to proceed without it.
- I found that the Alien only twice got into the vents to get me (this was towards the end), so if you're hiding in the vent system it's best to hide in a corner (i.e. where there's an L turn) so you can keep an eye on both directions.
- Missions 10, 14 and 16 were the most painful, and they're also some of the longest levels, so be prepared for a long slog. Don't be discouraged.
- Save Often! The game design has luckily put save points in a lot of places and generally before the more difficult parts, so while you may be reloading from one particular save point often, you're keeping your backtracking to a minimum. The game DOES save collectable pickups when you reload the to your last save, but always find a save point when you're done with your session.
- Two important tips for Mission 18: