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.
Share a weapon in MP
Craft all items
Kill all animal types and display heads
Play through entire game without killing or eating animals. Alone in Single Player or together in Multiplayer.
Craft 10 medicine items
Explore all caves
Build a super long wall
Pass 50,000 steps
Repair a shelter
Cut down 1000 trees
Catch fish with a trap. Alone in Single Player or together in Multiplayer.
Eat all mushroom types
Kill shark. Alone in Single Player or together in Multiplayer.
Cut down 100 trees
Killed downed enemy with rock
Knock down 6 or more trees with 1 explosive. 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
Collect all robot pieces
Find all missing passengers
Make and wear stealth armour
Eat an entire family
Set off 20 bombs
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Grow all plant types
Collect all cassette tapes!
Revive 10 co-op players
Use the compass
In Single Player, kill 100 cannibals
Chop up 50 bodies
Revive one co-op player
Survive 5 nights
Share a food or drink item in MP
Kill bird with arrow
Eat an enemy
Sleep on yacht
Sleep with another player (group sleep)
Kill a bunny. Alone in Single Player or together in Multiplayer.
Survive 1 night