There is a moment early in the game where Shantae's Uncle describes the 4 playstyles of an adventurer.
Basically what he means by his description there are people who Complete the game, People who complete the game 100%, People who Speed run the game Any%, and people who Speed Run the game 100%
This achievement is for pulling off a 100% Speed Run.
This game considers a 100% speed run as
All Squid Hearts Collected (They don't need to be melted)
All Dark Magic Collected.
All Abilities Purchased from the Shop
Beating the game Under 3 Hours. (An extra Hour than Any% Speed Run)
I recommend you attempt this achievement on New Game+ (Pirate Mode).
On Pirate Mode Shantae starts with all of the Pirate Weapons which makes skipping a lot of areas very possible.
Here are some tricks that will help you shave off time on your speed run.
NOTE: Don't OOB glitch skipping the petrify spell on the 100% run only on the any% run