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