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