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