For this achievement you need to complete the three campaigns: Human, Alien, Predator.
The Human campaign contains six levels:
1 - Colony
2 - Refinery
3 - Jungle
4 - Ruins
5 - Labs
6 - Pyramid
The Predator campaign contains six levels:
1 - Tutorial
2 - Jungle
3 - Refinery
4 - Ruins
5 - Labs
6 - Pyramid
The Alien campaign contains five levels:
1 - Labs
2 - Colony
3 - Refinery
4 - Jungle
5 - Ruins
Campaigns can be completed in any order for the achievement to be unlocked, as long as all levels are completed.