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