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