Here is the full list of all 26 Dimensional Animals achievements.
You entered a mysterious portal and found the beautiful Cobalt Forest
Bingo's worst nightmare came to life in Nightmare Land
You entered a portal and reached a new sub-area of Pristine Beach
You defeated the "giantest" crab of Pristine Beach
You defeated the creature behind the giant bush, wishing it kept hidden
You defeated the veterinarian haunting Bingo's nightmares
You rematched Clawbert's Dad and won, in a hidden sub-area of Pristine Beach
You rematched Cespuglio Bolshoi and won, in a hidden sub-area of Cobalt Forest
You rematched Joana and won, in a hidden sub-area of Nightmare Land
You defeated 20 Clawberts in Pristine Beach
You defeated 5 Jowlsons in Pristine Beach
You defeated 20 Stellarios or Spiksters
You defeated 10 Bustealths in Cobalt Forest
You defeated 20 Isnaels in Cobalt Forest
You defeated 15 Boblobs in Nightmare Land
Well done! You collected all 50 diamonds
Amazing! You collected all 25 life orbs
Incredible! You explored 100% of the map
Good job! You completed the game on Normal Mode
Fantastic! You completed the game on Plus Mode
You fused with Fidget! His name is inspired by fidget spinners
You fused with Scott! His name is inspired by a beloved cat of mine who unfortunately passed away
You fused with Papo! His name is inspired by a plushie my wife had as a baby
You fused with Tucker! He is a character from Rift Racoon, a previously launched game of mine
Mamma Mia! You defeated a Referencio in Cobalt Forest
You absorbed 1000 health pickups