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