Here is the full list of all 45 The Forest achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Play through entire game without killing or eating animals. Alone in Single Player or together in Multiplayer.
In Single Player, don't kill any cannibals for more than 10 days in a row
Finish Game
Craft all items
Make and wear stealth armour
Explore all caves
Find all missing passengers
Collect all cassette tapes!
Collect all robot pieces
Build a super long wall
Cut down 1000 trees
Set off 20 bombs
Revive 10 co-op players
In Single Player, kill 100 cannibals
Eat an entire family
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Chop up 50 bodies
Kill all animal types and display heads
Eat all mushroom types
Pass 50,000 steps
Craft 10 medicine items
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Repair a shelter
Sleep on yacht
Grow all plant types
Cut down 100 trees
Eat an enemy
Killed downed enemy with rock
Survive 5 nights
Kill a bunny. Alone in Single Player or together in Multiplayer.
Kill shark. Alone in Single Player or together in Multiplayer.
Share a food or drink item in MP
Catch fish with a trap. Alone in Single Player or together in Multiplayer.
Use the compass
Kill bird with arrow
Revive one co-op player
Share a weapon in MP
Sleep with another player (group sleep)
Survive 1 night