Here is the full list of all 12 The Defender: Farm and Castle achievements.
You can beat the boss
Archer attack (base damage) over 7,000
You have reached level 100
You have reached level 90
You have reached level 80
You have reached level 70
You have reached level 60
You have reached level 50
You have reached level 40
You have reached level 30
You have reached level 20
You have reached level 10