Xenomorphs? You eat 'em for breakfast. Scraping out its carapace with a spoon, between mouthfuls of acidic meatgoop you try to launch a lecture on how actually "xenomorph" isn't its name. That's just how tough you are. For you, dear friend, I have a treat. Alien: Isolation has added two new difficulty modes, including one aimed at making everything a whole lot tougher.
Alternatively, if you've steered clear of Isolation because the very idea of it send a chill down your spine and sets your skin a-crawling, the other mode makes it all easier so you can more freely tour and world and follow the story. You're never wholly safe, though.
Novice difficulty makes the alien less aggressive, a slower learner, easier to distract, and not as good as searching hiding places, while turning other enemies easier to defeat, making Ripley tougher, and throwing more items at her.
Nightmare mode, hooo. The motion tracker is wonky and often unreliable. The flamethrower gets less fuel and burns it quicker. You'll find less items and ammo. Systems are harder to hack. Androids hit like, well, mechanical men should. No health bar, no ammo counter. And a more clever, more aggressive alien. That's not even all of it. Good luck with that.
If you dig those 'posters' in that blog post, by the way, you can download hi-res versions over here.