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