To unlock the Not a toy anymore trophy in A Plague Tale: Innocence, you will need to fully upgrade the sling.
You will be introduced to crafting in Chapter 2 "The Strangers". Once you have access to crafting, you can upgrade the sling at workbenches or by pressing the TouchPad to access the crafting menu at any time.
To fully upgrade the sling, you will need to upgrade both the Strings and Pouch categories three times each:
Strings:
- First upgrade: Hitting enemies in the head kills them instantly
- Second upgrade: Reduces initial load time for Amicia's sling
- Third upgrade: The sling no longer makes any noise
Pouch:
- First upgrade: Reduces the time it takes to achieve maximum accuracy
- Second upgrade: Reduces reloading time
- Third upgrade: Allows two consecutive shots without priming and reloading
None of the items required for crafting are especially rare, but you will need to make sure you explore thoroughly to make sure you have everything required. If you finish the game and find you haven't got enough materials to upgrade the sling fully, you can replay Chapters 9 -12, which have a lot of the materials needed.