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.
Complete chapter 1
Complete chapter 2
Complete chapter 3
Complete chapter 4
Complete chapter 5
Complete chapter 6
Complete chapter 7
Complete chapter 8
Complete chapter 9
Complete chapter 10
Complete chapter 11
Complete chapter 12
Complete chapter 13
Complete chapter 14
Complete chapter 15
Complete chapter 16
Complete all chapters
Find all flowers
Find all feathers
Open all the secret chests
Recall all souvenirs
Fully upgrade the sling
Fully upgrade the crossbow
Fully upgrade the gear
Fully upgrade the instruments
Fully upgrade the alchemy
Extinguish 40 fires
Craft 100 ammunitions
Fully improve the Prudence skills
Fully improve the Aggressive skills
Fully improve the Opportunism skills
Shoot all the pine cones
Successfully complete all throws in the Crowns game
Interact with all the old protector’s items in the sanctuary
Don't kill the guard on the docks