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