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