Below I have all 38 achievements broken up into sections. The story and boss achievements you cannot miss if you play through the entire game. The harder achievements will be down towards the bottom. I tried keeping them in order, but if anything needs to be rearranged or corrected please let me know so that I can make the corrections.

Welcome to Arena Town
Arrive at Arena Town and speak to the mayor.


Hidden Village
Find the Hidden Village.


Raise Sea Level
Get the valve from your Uncle and attach it to a machine to raise the water level.


Truly Tell-Tale
Obtain the lucky amulet from the scientist in the mossy biome.


Underwater Explorer
Enter the sea lab for the first time.


A Fortified Front
Arrive at Armor Town.


Duped!
You fell for a double cross!


Sunken Ship
Locate the sunken ship remains.


Dangerous Dances
Learn all the fusion dances from the other half genies


That's the Spirit!
Complete the ghostly quest.


Final Form
Obtain all the magical forms.


Shut Down
Deactivate the four towers.

A rose by any other name...
Defeat the first Siren.


Mega Busted
Defeat the second Siren.


Not Worm Food
Defeat the third Siren.


Tangle with the Angle
Defeat the fourth Siren.


A real brain buster
Defeat the fifth Siren.


Larger than Life
Defeat the sixth and final Siren.

Second Sight
All you need to do is reveal a hidden enemy by using the Seer Dance.


Sheer Perfection?
For this one you need to use the Refresh Dance on a rag and bones. These can be found in labyrinth 4, 5, and 6.


Refreshing Rewards
Use the Refresh Dance on a sickly silverfish. These can be found in labyrinth 3 and 5.


Shocking Solution
Open a shock machine by using the Shock Dance.


Fully Charged
Open every single shock machine.


It's Electrifying!
Use the Shock Dance on a circus squid when it is on the pole in labyrinth 5.


Hidden Treasure
Use the Quake Dance to reveal hidden treasure. You can use the Seer Dance to locate these.


Ancient Discoveries
Use the Quake Dance to reveal all of the buried statues.

All Sales Final
You just need to buy every upgrade from the shops to their max level.


Contest Winner
In the hidden village, go to the hut in the upper left corner and talk to the woman inside to start a dancing mini game. You will need to pay 10 coins to participate. In the mini game you need to strike a pose under the totems above you. A star will fly upwards and hit a totem to remove it. To get this achievement you need to do this 10 times in a row without missing once! You only get 5 shots per try so once you are out of shots just pay the cost again. The minimum cost you will have to pay is 20 coins.


Slime Time
Slimes will change color each time you hit them. You need to use a fusion dance on each color to get this achievement. Seer Dance when it is purple, Refresh Dance when it is green, Shock Dance when it is yellow, and Quake Dance when it is red.


Squid Saver
Here you need to find every heart squid in the game, but instead of using them to increase your total life you need to keep them in your inventory for the entire game. There are 36 heart squids in total.


Sight Unseen
While exploring the map, there will be three rooms where a lobster girl is peeking through a window. Do not scare her! In order to do this you need to crawl through the room. If you do not scare her in all three rooms, you will get the achievement when she reveals herself towards the end.


Collector
Obtain a monster card by killing a monster and picking up its dropped card.


A Full Set
Have three monster cards equipped at once.


Complete Collection
Collect 1 copy of every single monster card.


A New Challenge
Complete the game in Beginner or Definitive Mode.


Card Shark
Complete the game in Rule Breaker or Full Deck Mode.

Saving the Day
Complete the game. You do not need to collect everything and you do not need to speed run for this.


Turned over every rock
Complete the game with 100% completion. You need to collect all heart squids and nuggets. No time limit required.


In the blink of an eye
Complete the game in under 4 hours. You do not need to collect everything for this speed run.


Could use a vacation
Complete the game in under 6 hours while collecting all heart squids and nuggets.