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