Here is the full list of all 6 Endless TD achievements.
The base game contains 0 achievements, and there is 1 DLC pack containing 6 achievements.
Defeat 100.000.000 (1 Million) enemies.
Defeat 100.000 (100 Thousand) bosses.
Reach wave 100.000 (100 Thousand) on easy difficulty.
Reach wave 1.000.000 (1 Million) on normal difficulty.
Reach wave 10.000.000 (10 Million) on hard difficulty.
Reach Wave 100.000.000 (100 Million) on impossible difficulty.