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