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.
Eat an enemy
Find all missing passengers
Catch fish with a trap. Alone in Single Player or together in Multiplayer.
Repair a shelter
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Finish Game
Killed downed enemy with rock
Explore all caves
Chop up 50 bodies
Collect all robot pieces
Eat all mushroom types
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Collect all cassette tapes!
Sleep on yacht
Set off 20 bombs
Craft 10 medicine items
Kill bird with arrow
Use the compass
Kill a bunny. Alone in Single Player or together in Multiplayer.
Make and wear stealth armour
Revive one co-op player
In Single Player, kill 100 cannibals
In Single Player, don't kill any cannibals for more than 10 days in a row
Cut down 100 trees
Survive 5 nights
Survive 1 night
Sleep with another player (group sleep)
Eat an entire family
Share a food or drink item in MP
Share a weapon in MP
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.
Revive 10 co-op players
Build a super long wall
Kill shark. Alone in Single Player or together in Multiplayer.
Pass 50,000 steps
Cut down 1000 trees