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