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