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.
Sleep with another player (group sleep)
Revive 10 co-op players
Revive one co-op player
Killed downed enemy with rock
Share a food or drink item in MP
Share a weapon in MP
Play through entire game without killing or eating animals. Alone in Single Player or together in Multiplayer.
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.
Pass 50,000 steps
Cut down 1000 trees
Finish Game
Explore all caves
Kill all animal types and display heads
Collect all robot pieces
Repair a shelter
Kill shark. Alone in Single Player or together in Multiplayer.
Find all missing passengers
Build a super long wall
Sleep on yacht
Set off 20 bombs
Collect all cassette tapes!
Craft 10 medicine items
Craft all items
Eat all mushroom types
Cut down 100 trees
In Single Player, kill 100 cannibals
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Grow all plant types
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Kill bird with arrow
Chop up 50 bodies
Eat an entire family
Survive 5 nights
Eat an enemy
Kill a bunny. Alone in Single Player or together in Multiplayer.
Make and wear stealth armour
Use the compass
Survive 1 night