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.
Kill shark. Alone in Single Player or together in Multiplayer.
Pass 50,000 steps
Cut down 1000 trees
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Killed downed enemy with rock
Chop up 50 bodies
Catch fish with a trap. Alone in Single Player or together in Multiplayer.
Grow all plant types
Craft 10 medicine items
In Single Player, kill 100 cannibals
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Share a weapon in MP
Make and wear stealth armour
Eat an enemy
Kill a bunny. Alone in Single Player or together in Multiplayer.
Sleep on yacht
Set off 20 bombs
Finish Game
In Single Player, don't kill any cannibals for more than 10 days in a row
Kill bird with arrow
Use the compass
Survive 5 nights
Repair a shelter
Cut down 100 trees
Revive 10 co-op players
Collect all cassette tapes!
Share a food or drink item in MP
Revive one co-op player
Sleep with another player (group sleep)
Survive 1 night
Eat an entire family
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
Build a super long wall
Find all missing passengers
Eat all mushroom types
Collect all robot pieces