Here is the full list of all 35 A Plague Tale: Innocence achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Save a soldier
Play hide-and-seek
Complete all chapters
Complete chapter 16
Find Rodric's forge
Complete chapter 15
Complete chapter 14
Complete chapter 13
Find 6 flowers
Find 13 curiosities
Complete chapter 12
Complete chapter 11
Complete chapter 10
Complete chapter 9
Complete chapter 8
Find the tomb
Complete chapter 7
Craft 100 ammunitions
Complete chapter 6
Complete chapter 5
Complete chapter 4
Complete chapter 3
Complete chapter 2
Find a lunch for Hugo
Complete chapter 1
Find all the flowers
Find all curiosities
Find all the gifts for the orphans
Fully upgrade the sling
Fully upgrade the equipment
Enter into the 5 alchemist carts
Complete the aiming training
Enter through the main door
Save the dying
Stay with the captain