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