The Invincible

When at The Camp you will find Krauta in the far tent, this is when you get in contact with Novik who will be with you for the rest of the story. Novik will get you doing a few tasks inside the tent and then you can head out. When outside the tent Novik will try to make you find the other crew members but we don't want to do this, so go through the dialogue and when the option comes be sure to select 'I'm not leaving Krauta alone like this'. This will ensure we rescue Krauta and also be our first crew member saved for the other achievement.
This achievement won't pop until we reach memory 5 later in the story, just after the lava area after finding the broken probe that joins us.

If you need more help with this you can follow my video guide below which will cover this achievement:

This is part of I Leave No Man Behind Achievement / Trophy

Here's my video guide: