Here is the full list of all 17 Dandy & Randy DX achievements.
Defeat Otis the Octopus.
Defeat Caca The Desert Monster.
Defeat The Dusk Ghost.
Defeat Natalia No Good.
Defeat The Dig Machine.
Defeat Edward Tall.
Finish The Game.
Find the Boomerang
Find the Hammer.
Find the Hookshot.
Find the Running Shoes.
Find 15 hidden coins in a single level.
Get at least $1000 (total).
Get at least $5000 (total).
Get at least $7500 (total).
Unlock Sally.
Unlock Molly.