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