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