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