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