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