Here is the full list of all 34 They Are Billions achievements.
1 Million infected killed!
500.000 infected killed!
Build a colony with 5.000 colonists.
Build a colony with 10.000 colonists.
100.000 infected killed!
Win a Survival game on Easy mode.
Build the six wonders in your colony.
50.000 infected killed!
Build a colony with 2.000 colonists.
Build a colony with 1.000 colonists.
Kill an Infected Giant.
10.000 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 Accesible mode.
Win a Survival game on Challenging mode.
Win a Survival game on Brutal mode.
Kill two Infected Giant on the same map.
Kill three Infected Giant on the same map.
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.