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.
Eat an entire family
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.
Sleep on yacht
Explore all caves
Build a super long wall
Make and wear stealth armour
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Finish Game
Find all missing passengers
Kill shark. Alone in Single Player or together in Multiplayer.
Eat all mushroom types
Pass 50,000 steps
Set off 20 bombs
Repair a shelter
Collect all robot pieces
Cut down 1000 trees
In Single Player, don't kill any cannibals for more than 10 days in a row
Catch fish with a trap. Alone in Single Player or together in Multiplayer.
Eat an enemy
Chop up 50 bodies
Collect all cassette tapes!
Survive 5 nights
In Single Player, kill 100 cannibals
Craft 10 medicine items
Kill bird with arrow
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Use the compass
Revive 10 co-op players
Cut down 100 trees
Killed downed enemy with rock
Sleep with another player (group sleep)
Survive 1 night
Share a food or drink item in MP
Share a weapon in MP
Kill a bunny. Alone in Single Player or together in Multiplayer.
Revive one co-op player