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