Here is the full list of all 40 Shantae and the Seven Sirens achievements.
Complete the game in Rule Breaker or Full Deck Mode.
Complete the game in Beginner or Definitive Mode.
Complete the game without any Health upgrades and all Heart Squids collected.
Collect all Monster Cards.
Avoid startling the Lobster Girl throughout the adventure.
Turn an enemy to an ally by helping them heal.
Complete the adventure with 100% completion as quickly as possible!
Complete the adventure with 100% completion!
Open all Shock Machines.
Unearthed all secrets.
Complete the adventure as quickly as possible!
Witness every magical outcome with Slimes.
Shock a circus squid.
Revitalize cellular functions.
Complete the adventure!
Defeated the Empress Siren.
Uncovered a possible threat.
Deactivate all the Towers.
Defeated the fifth Siren.
Obtain all magical forms.
Unearth a buried treasure.
Complete a Ghostly Quest.
Upgrade all magic to max.
Learn all magical dances.
Defeated the fourth Siren.
Locate the sunken ship remains.
Fell for a double cross.
Open a Shock Machine.
Ascend to Armor Town.
Win the highest total in a Hula Contest.
Defeated the third Siren.
Enter the Sea Lab.
Obtain the Lucky Amulet.
Defeated the second Siren.
Use the valve.
Reach Tree Town.
Have three Monster Cards equipped at once.
Defeated the first Siren.
Took the tour!
Obtain a Monster Card.