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