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