Here is the full list of all 29 Citizens Unite!: Earth x Space achievements.
Recruit 5 Citizens in each era
Recruit 25 Citizens in each era
Recruit all 88 Citizens across both eras
Get one Citizen in each era to Talent level 3
Get five Citizens in each era to Talent level 3
Get all Citizens from both eras to max Talent level
Defeat 1,000 enemies in each era
Deal 10,000 damage in combat in each era
Receive 10,000 damage in combat in each era
Find 100 treasures in each era
Discover 20 locations in each era
Discover 40 locations in each era
Earn $10,000 in Citizens of Earth and 10,000 credits in Citizens of Space
Spend $10,000 in Citizens of Earth and 10,000 credits in Citizens of Space
Collect 100 items in each era
Collect 300 items in each era
Use 50 items in each era
Use 100 items in each era
Recruit VP in Citizens of Space
Recruit Ambassador in Citizens of Earth
Return the first Book of History in each Era
Return 5 Books of History in each Era
Return all books of History in each Era
Retrieve one treasure in each Era revealed from returning Books of History
Retrieve five treasures in each Era revealed from returning Books of History
Retrieve all of the treasures revealed from returning Books of History in both eras
Unlock all achievements