Here is the full list of all 34 They Are Billions achievements.
100 Millions infected killed!
Win a Survival game on Brutal mode.
Win a Survival game (Score Factor >= 200%) without using Attack Towers like Ballista or Executor.
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.
50 Millions infected killed!
10 Millions infected killed!
5 Millions infected killed!
2 Millions infected killed!
1 Million infected killed!
500.000 infected killed!
Build a colony with 2.000 colonists.
Build a colony with 5.000 colonists.
Build a colony with 10.000 colonists.
Build a colony with 1.000 colonists.
Win a Survival game on Easy mode.
Build the six wonders in your colony.
Kill three Infected Giant on the same map.
Kill two Infected Giant on the same map.
100.000 infected killed!
Kill an Infected Giant.
Win a Survival game on Challenging mode.
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 >= 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.
50.000 infected killed!
10.000 infected killed!
Win a Survival game on Accesible mode.