Main storyline achievement, unmissable. Unlocks at the credit screen when you complete all areas of the game:
Luckily the DLC is MUCH, MUCH
shorter than the base game - and it's a lot easier as well.
Here is a NO Out Of Bounds SPEED RUN
: approx. 25 minutes!
There are a couple times he saves/exits/reloads - you don't need to do this - it simply skips the cutscenes...