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