Here is the full list of all 35 A Plague Tale: Requiem achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Fully improve the Prudence skills
Fully improve the Aggressive skills
Fully improve the Opportunism skills
Fully upgrade the instruments
Fully upgrade the gear
Shoot all the pine cones
Complete all chapters
Complete chapter 16
Find all flowers
Complete chapter 15
Complete chapter 14
Complete chapter 13
Fully upgrade the crossbow
Open all the secret chests
Find all feathers
Extinguish 40 fires
Recall all souvenirs
Fully upgrade the sling
Complete chapter 12
Complete chapter 11
Complete chapter 10
Fully upgrade the alchemy
Complete chapter 9
Interact with all the old protector’s items in the sanctuary
Complete chapter 8
Successfully complete all throws in the Crowns game
Complete chapter 7
Complete chapter 6
Complete chapter 5
Craft 100 ammunitions
Complete chapter 4
Don't kill the guard on the docks
Complete chapter 3
Complete chapter 2
Complete chapter 1