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