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