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