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