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 Cabin Ambush
Complete 30 Minutes or Less
Complete Invasion of Privacy
Unlock Steve
Unlock Erica
Complete Hospital Brawl
Complete Ivan the Smuggler
Found 25 hidden gnomes. Half-way there!
Unlock Will
Complete Revenge of the Geeks
Unlock Hopper and Joyce
Unlock Eleven
Complete Chores for Granny Perkins
Successfully hack the hardest level chest/door
Craft 5 trinkets
Unlock Max
Complete Break In, Make Out
Unlock Jonathan
Unlock Nancy
Complete Store Raid
Complete Wall Flower
Complete Rats in the Walls
Complete On the Wire
Complete Radar Love
Unlock Dustin
Crafted your first item
Complete Sneak Peek