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