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.
Find all feathers
Find all flowers
Recall all souvenirs
Extinguish 40 fires
Fully improve the Aggressive skills
Open all the secret chests
Fully upgrade the sling
Fully upgrade the crossbow
Fully upgrade the gear
Fully upgrade the instruments
Fully upgrade the alchemy
Fully improve the Prudence skills
Fully improve the Opportunism skills
Successfully complete all throws in the Crowns game
Complete all chapters
Complete chapter 16
Complete chapter 15
Complete chapter 14
Complete chapter 13
Complete chapter 12
Complete chapter 11
Complete chapter 10
Complete chapter 9
Interact with all the old protector’s items in the sanctuary
Complete chapter 8
Complete chapter 7
Complete chapter 6
Craft 100 ammunitions
Complete chapter 5
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