It sounds like you're referring to a research paper or analysis focused on the in the context of all achievements being updated (possibly for a game like Minecraft with modded content, or a specific tech/magic mod pack).
Precision is key here. Use the piston to hit a mob directly on the top of the head ; side hits don't count.
Craft and sell a (requires wood and hide) to unlock the Skeleton character and Ritual background. Jack-o'-Lantern Girl
, the path to 100% completion is now a dense saga of crafting, trading, and redstone experimentation.
