Here is the full list of all 50 Citizens of Earth achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Defeat the Secretary Supreme.
Use 75 items.
Recruit 25 citizens.
Defeat the Alien Commander.
Defeat the Mishmasher.
Collect 300 items.
Defeat Honcho Villa.
Defeat DJ Voodoo.
Spend $10,000.
Defeat Agent D.O.O.M.
Defeat Colonel Cookie.
Use 25 items.
Receive 2,500 damage in combat.
Find 100 treasures.
Defeat the Hippie Guru.
Spend $3,000.
Earn $10,000.
Defeat 250 enemies.
Spend $1,000.
Discover 30 locations.
Find 45 treasures.
Collect 100 items.
Deal 10,000 damage in combat.
Get one citizen to Lv 20.
Defeat the Puppet President.
Get one citizen to Talent Lv 3.
Earn $3,000.
Discover 20 locations.
Defeat Mr. Mocha.
Discover 10 locations.
Deal 2,500 damage in combat.
Collect 30 items.
Receive 500 damage in combat.
Find 15 treasures.
Recruit 5 citizens.
Defeat 50 enemies.
Deal 500 damage in combat.
Earn $1,000.
Defeat the Opposition Leader.
Defeat 1,000 enemies.
Receive 10,000 damage in combat.
Recruit all 40 citizens.
Use 150 items.
Earn $100,000 in the Casino.
Enroll 9 citizens simultaneously in School.
Get all citizens to Lv 30.
Ambush 10 enemies in a row.
Complete all Wanted Poster quests.
Complete all Extermination quests.
Complete all Photography quests.