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