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