Here is the full list of all 20 Dungeons & Geese achievements.
Complete 1'st Level
Defeat Boss in 1'st location
Defeat Boss in 2'st location
Defeat Boss in 3'rd location
Complete 18'th level
Complete the Game
Complete 36th level
Kick out all guests from the ball
1st Ending
2nt Ending
3rd Ending
4rd Ending
Meet Lacroix in Heaven
Collect 100 Pink Spears
Collect 50 Blue Spears
Collect 10 Heal Items
Run the game
Solve the mystery behind Old's Man Bankruptcy
It's better than goose saddling you, isn't it?