Here is the full list of all 69 Squirm achievements.
The base game contains 66 achievements, and there is 1 DLC pack containing 3 achievements.
Beat the game.
Start looking for your purpose.
That can't be all, could it?
Defeat Float.
Open the box...
Enter the inverse world.
See something you weren't meant to see.
Create a black hole by shooting a sun.
Get a star in space... where they belong.
Collect all 6 stars!
Are you sure you know how to pilot this thing?
Reach the top of the green tower and get the key!
Get all 100 coins in the green tower.
Explode...
Get the star in "The Green Tower".
Remember me?
Kill Blocka.
Get the star in "The Blistering Castle".
That's messed up...
Ruler of his people!
Burn to death.
Kill King Fatty.
Oopsie!
Get the star in "The Azurine Glacier".
Collect half of the stars.
Die 100 times.
Kill Skelord.
Get the DOUBLE JUMP!
Fall into the shadows...
Get the star in "The Spookileum".
Complete the surprise party world!
Die to spikes.
Enter the surprise party world!
Kill Dr. Ludo.
Get the GUN!
Get the star in "The Workplace".
He was past his expiration date anyway...
...fond of drink and industry.
!!!
The best jokes are inside jokes!
Fart 100 times.
Beat the game in under 2 hours.
...eeeeeeeeeeee
Beat the game in under 1 hour and 40 minutes.
Beat the game in under 1 hour and 20 minutes.
Beat the game in under 1 hour.
Beat the game in under 1 hour. Including Purpose!
Beat the game in under 45 minutes. Including Purpose!
Get 0 coins in the green tower.
...
Enter "The Mirror Tower".
Take a look. It's in a book!
Beat zone 1 as Squim.
Beat zone 2 as Squim.
Beat zone 3 as Squim.
Beat zone 4 as Squim.
Rescue Crackers!
Click the 100% button on the main menu.
Defeat the Rainbow Sun and enter "The Rainbow Nexus' Core".
Three years later... one last challenge awaits: The Rainbow Nexus!
I guess he couldn't make up his mind...