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