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