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