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