First and foremost, this guide will not differentiate between the playthrough on Hard vs. the one on Novice, in case you want to capture all achievement in a single playthrough.
The game contains various collectibles, namely ID Tags, Nostromo Logs, and Archive Logs. You will need to find all ID Tags (50), all Nostromo Logs (10), and 100 Archive logs out of 172 for the following three achievements:
Collect 10 Nostromo logs in the main campaign
It is highly recommended that you follow a video guide for all collectibles, as several require detours from the main storyline. The following YouTube video contains all collectibles and shows how to get them in detail - credit goes to TA user Zasta 360 GameTV!
The walkthrough will use spoiler tags if you don't want the story to be spoiled too early.
If you have followed this guide, you should only be missing two achievements by now, 100 Times Too Many and Self Defense. I suggest that you use your second playthrough to kill ten (hostile) humans for Self Defense, as it can make proceeding through different areas easier. In any case, the grind for 100 Times Too Many will earn you Self Defense along the way.
Load up mission 17 - Desolation and set the difficulty to Nightmare. Equip your shotgun while in the elevator, then sprint towards the security guard patrolling the area. Pump him with lead. This is almost guaranteed to attract the Alien; if it doesn't, keep shooting with all you have until the Alien shows up. As soon as it does, succumb to your fate and let it kill you. Rinse and repeat. You can keep track of your progress by periodically checking the Xbox One Achievements App - e.g. 20% progress for Self Defense means you have killed two humans and have eight to go; e.g. 41% progress for 100 Time Too Many means you have been killed by the Alien 41 times and have 59 to go. Note that only kills by the Alien count, not other deaths caused by humans, Synthetics, explosions, or transit cars.
After killing the security guard ten times (or less, depending on your previous playing style), you will earn:
After getting killed by the Alien 100 times altogether, you will earn:
This concludes it - congratulations to a well-deserved 1000 Gamerscore!
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