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