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.
Pass 50,000 steps
Find all missing passengers
Explore all caves
Eat all mushroom types
Collect all cassette tapes!
Craft all items
Kill all animal types and display heads
Set off 20 bombs
Collect all robot pieces
Kill shark. Alone in Single Player or together in Multiplayer.
Build a super long wall
Cut down 1000 trees
Craft 10 medicine items
Share a weapon in MP
Killed downed enemy with rock
Catch fish with a trap. Alone in Single Player or together in Multiplayer.
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Make and wear stealth armour
Revive 10 co-op players
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Eat an entire family
Eat an enemy
Finish Game
Share a food or drink item in MP
Repair a shelter
In Single Player, don't kill any cannibals for more than 10 days in a row
Grow all plant types
Revive one co-op player
Sleep on yacht
In Single Player, kill 100 cannibals
Chop up 50 bodies
Use the compass
Cut down 100 trees
Kill a bunny. Alone in Single Player or together in Multiplayer.
Survive 5 nights
Kill bird with arrow
Sleep with another player (group sleep)
Survive 1 night