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