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