Here is the full list of all 12 The Defenders: The Second Wave achievements.
Struck the moon
Killed at least ten butterflies
Won the game on Normal difficulty
Tanked 1000 hit points without dying
Parried 50 enemy projectiles
Won the game on "Easy" difficulty
Have used over 3500 mana
Killed at least 1000 enemies
50 kills without taking damage
Started a game
Unlocked trial mode, because the game is so good =)
Won the game on Hard difficulty