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