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