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.
Explore all caves
Craft all items
Find all missing passengers
Pass 50,000 steps
In Single Player, kill 100 cannibals
Cut down 1000 trees
Kill shark. 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.
Kill all animal types and display heads
Catch fish with a trap. Alone in Single Player or together in Multiplayer.
Finish Game
Collect all cassette tapes!
Eat all mushroom types
Collect all robot pieces
Set off 20 bombs
Craft 10 medicine items
Build a super long wall
Sleep on yacht
Killed downed enemy with rock
Kill a bunny. Alone in Single Player or together in Multiplayer.
Use the compass
Repair a shelter
Chop up 50 bodies
Eat an entire family
In Single Player, don't kill any cannibals for more than 10 days in a row
Eat an enemy
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Kill bird with arrow
Grow all plant types
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Cut down 100 trees
Survive 5 nights
Revive 10 co-op players
Make and wear stealth armour
Revive one co-op player
Share a weapon in MP
Survive 1 night
Sleep with another player (group sleep)
Share a food or drink item in MP