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