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