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