Here is the full list of all 35 Age of Civilizations II achievements.
Join 50 alliances
Create 50 unions
Join 25 alliances
Create 25 unions
Join 10 alliances
Join 5 alliances
Create 10 unions
Create 5 unions
Create union
Create 50 vassals
Create 20 vassals
Create 5 vassals
Adopt the Monarchy government
Adopt the ideology of Communism
Adopt the ideology of the City State
Adopt the ideology of democracy
Adopt the Horde ideology
Adopt Republic ideology
Form Russian Empire
Adopt Fascism ideology
Capture 1500 provinces
Form Japan
Form Australia-Hungary
Form Ottoman Empire
Capture 750 provinces
Capture 500 provinces
Form Italy
Join alliance
Capture 300 provinces
Form Austrian Empire
Create a vassal
Capture 150 provinces
Capture 75 provinces
Capture 30 provinces
Capture 10 provinces