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