Here is the full list of all 20 Doodle Tanks achievements.
Bölter created
Unlocked all Germany events
Unlocked the PaK 44 L/55 and KwK 44 L/38 guns
Maus created
Unlocked all elements of Germany
Unlocked Panther, Tiger I, Tiger II
All TDs created
Unlocked the Pz III and Pz IV tanks
All light tanks created
All T-34 unlocked
T-34, KV-2, IS-4 tanks unlocked
All medium tanks created
All USSR elements unlocked
All inventions created
First tank created
8 groups created
All Lend-Lease supplied tanks unlocked
25 elements unlocked
T-34 unlocked
50 elements unlocked