Here is the full list of all 31 Stranger Things 3: The Game achievements.
Beat the game on New Game+
Found all 50 hidden gnomes.
Complete the game
Complete Mall Showdown
Complete 30 Minutes or Less
Complete Cabin Ambush
Complete Invasion of Privacy
Unlock Steve
Unlock Erica
Unlock Will
Complete Hospital Brawl
Found 25 hidden gnomes. Half-way there!
Unlock Eleven
Unlock Hopper and Joyce
Complete Ivan the Smuggler
Complete Chores for Granny Perkins
Successfully hack the hardest level chest/door
Complete Store Raid
Unlock Max
Unlock Jonathan
Unlock Nancy
Craft 5 trinkets
Complete Wall Flower
Complete Break In, Make Out
Complete Rats in the Walls
Complete On the Wire
Complete Radar Love
Crafted your first item
Complete Revenge of the Geeks
Unlock Dustin
Complete Sneak Peek