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