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