Here is the full list of all 20 GLAD VALAKAS TOWER DEFENCE 2 achievements.
Kill the boss
Complete 3 wave of 4 chapter
Complete 2 wave of 4 chapter
Complete 1 wave of 4 chapter
Complete 2 wave of 3 chapter
Complete 3 wave of 3 chapter
Complete 1 wave of 3 chapter
Complete 3 wave of 2 chapter
Complete 2 wave of 2 chapter
Complete 1 wave of 2 chapter
Complete 3 wave of 1 chapter
Complete 2 wave of 1 chapter
Complete 1 wave of 1 chapter