Here is the full list of all 34 Fall Guys achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Equip an uncommon or better Body Colour, Pattern, Upper and Lower Costume piece
Win an Episode with a custom Celebration equipped
Qualify from 100 rounds
Reach lvl 25 fame during a season
Get first place in a racing round 5 times
Perform an emote just before coming first in a race round
Qualify from a team game with a score of 1
Equip a legendary Body Colour, Pattern, Upper and Lower Costume piece
Reach lvl 10 fame during a season
Qualify from a racing round despite falling over more than 10 times
Win an Episode as part of a party of 3 or more players
Win your first Episode
Fall for at least 3 seconds before landing on your head
Bump into other Fall Guys 1000 times in total
Get first place in a racing round
Qualify from a round without falling over even once
Qualify after a round goes to overtime
Bump into 3 people while rolling on the ground before getting up
Share a hug with a Fall Guy
Knock someone over
Reach terminal velocity
Qualify from your first round
Equip your first cosmetic item
Unlock 50 cosmetic items from the store
Unlock 10 cosmetic items from the store
Equip a rare or legendary Body Colour, Pattern, Upper and Lower Costume piece
Equip your first legendary customization item
Reach lvl 40 fame during a season
Get first place in a racing round 20 times
Win 5 Episodes in a row
Win 7 Episodes
Win 20 Episodes
Qualify from 500 rounds
Clock up 1 hour total time falling