Here is the full list of all 14 Dandy Randy achievements.
Beat Otis the Octopus.
Beat Paul Matthews.
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).
Beat Natalia No Good.
Beat The Dusk Ghost.
Beat Caca The Desert Monster.