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