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