Here is the full list of all 34 They Are Billions achievements.
100.000 infected killed!
Build a colony with 5.000 colonists.
Build a colony with 10.000 colonists.
Win a Survival game on Easy mode.
50.000 infected killed!
Build a colony with 2.000 colonists.
Win a Survival game on Accesible mode.
Build a colony with 1.000 colonists.
10.000 infected killed!
500.000 infected killed!
1 Million infected killed!
2 Millions infected killed!
5 Millions infected killed!
10 Millions infected killed!
50 Millions infected killed!
100 Millions infected killed!
Win a Survival game on Challenging mode.
Win a Survival game on Brutal mode.
Kill an Infected Giant.
Kill two Infected Giant on the same map.
Kill three Infected Giant on the same map.
Build the six wonders in your colony.
Win a Survival game (Score Factor >= 100%) without using walls, gates and towers.
Win a Survival game (Score Factor >= 100%) with just Soldiers in your army. No Attack Towers allowed.
Win a Survival game (Score Factor >= 100%) with just Rangers in your army. No Attack Towers allowed.
Win a Survival game (Score Factor >= 100%) with just Snipers in your army. No Attack Towers allowed.
Win a Survival game (Score Factor >= 200%) without using Attack Towers like Ballista or Executor.
Win a Survival game (Score Factor >= 100%) with no new units trained.
Win a Survival game (Score Factor >= 100%) without pausing the game.
Win a Survival game (Score Factor >= 100%) with no casualties. No Attack Towers allowed.
Win The New Empire Campaign with a score of 10.000 victory points.
Win The New Empire Campaign with a score of 25.000 victory points.
Win The New Empire Campaign with a score of 40.000 victory points.
Win The New Empire Campaign with a score of 70.000 victory points.