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