Here is the full list of all 31 Stranger Things 3: The Game achievements worth 1,000 gamerscore.
Complete Wall Flower
Unlock Jonathan
Unlock Nancy
Complete On the Wire
Complete Radar Love
Crafted your first item
Unlock Dustin
Complete Sneak Peek
Complete Revenge of the Geeks
Complete Break In, Make Out
Complete Chores for Granny Perkins
Complete Hospital Brawl
Complete Cabin Ambush
Complete Mall Showdown
Complete 30 Minutes or Less
Complete Ivan the Smuggler
Complete Store Raid
Complete Rats in the Walls
Complete Invasion of Privacy
Successfully hack the hardest level chest/door
Unlock Eleven
Unlock Max
Unlock Erica
Unlock Steve
Unlock Hopper and Joyce
Found 25 hidden gnomes. Half-way there!
Acquire 5 trinkets
Unlock Will
Beat the game on New Game+
Complete the game
Found all 50 hidden gnomes.