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