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