Here is the full list of all 27 The Cave achievements worth 400 gamerscore. It takes around 12-15 hours to unlock all of the achievements on Xbox 360.
Saw every character's "bad ending". (Player 1 only)
Unlocked all Cave Paintings. (Player 1 only)
Got everyone out of The Cave without dying once.
Took all characters to the bottom of The Cave. (Player 1 only)
Saw every character's "good ending". (Player 1 only)
Played some dubious role in the Monk's murder of his Master.
Got the bridge inside the temple to collapse.
Stood by and watched as the Twins murdered their parents.
Watched Mummy and Daddy's furniture get broken all to bits.
Saw a postcard returned to the Gift Shop.
Got a Xavetar fortune for every character. (Player 1 only)
Shared in the blame for the Scientist's act of mass murder.
Saw someone slip off a ledge in the Missile Silo.
Came ever-so-close to recovering the Sarcophagus.
Pantomimed an ancient hieroglyph.
Reached the bottom of The Cave.
Saw every Can of Corn in The Cave destroyed.
Recorded and played back the elevator music from the Zoo food court.
Served as an accessory to the Time Traveler's murder of her enemy's ancestor.
Made all three characters smell like a dinosaur at once.
All three characters killed by one Miner's dynamite.
Enabled the Hillbilly to burn down the Carnival.
Got the Weight Guess scale to read 666.
Spied a King, eaten by a Dragon.
Helped the Knight obtain Excalibur.
Saw a postcard stolen from the Gift Shop.
Witnessed a hot dog cooked with the monster's breath.