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