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
Killed downed enemy with rock
Build a super long wall
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Find all missing passengers
Eat all mushroom types
Pass 50,000 steps
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.
Sleep on yacht
Revive 10 co-op players
Repair a shelter
Craft 10 medicine items
Cut down 100 trees
Chop up 50 bodies
Make and wear stealth armour
Kill shark. Alone in Single Player or together in Multiplayer.
Finish Game
Share a food or drink item in MP
Share a weapon in MP
Set off 20 bombs
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Eat an entire family
In Single Player, kill 100 cannibals
Kill bird with arrow
Collect all cassette tapes!
Revive one co-op player
Kill a bunny. Alone in Single Player or together in Multiplayer.
Eat an enemy
Sleep with another player (group sleep)
Use the compass
Survive 5 nights
Survive 1 night