Originally Posted by Achievement Guide
- Challenges add 0.10%
- Completing locations to 100% adds 0.03%
- Finding faction items adds 0.03%
- Resource crates add 0.01%
- Destroying military objects adds 0.005%
- Killing colonels adds 0.14%
If you haven't killed all the colonels yet, I recommend you do so as they add the most percentage. While you travel around in search for the colonels, you should also reach 100% completion in the areas you discover and pick up any faction items that are near you.
It definitely takes a while but with commitment and patience you will get there.