Here is the full list of all 15 Digging Dragon achievements.
complete the game
defeat Dungeon Lord
buy all the skins in the store
buy the first skin in the store
save up 1000 coins
build the 10th floor of the tower
save up 200 coins
save up 100 coins
build the first floor of the tower
defeat 100 enemies
defeat 50 enemies
win 50 skeletons
defeat 10 enemies
use a potion
you did't defeat Dungeon Lord