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