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