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