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