If you're following the walkthrough, it's important to know that you need hard ass level 10 skill when you go talk to Elizaveta when you are investigating Fletcher's escape.
So make sure you are building towards this with one of your characters from the start of the game. There are a few trinkets that can boost your hard ass skill, such as the MK III camera that you can find throughout your journey. Hold onto these, you may need them to clear that last level of skill.
Without skill level 10, the proper dialog options will not appear later in the story, which will negate the achievement.