Here is the full list of all 20 Spelunky achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
Rescue all 16 hidden characters.
Play Adventure Mode 1000 times.
Complete the game with at least two players alive. No shortcuts.
Complete the game the hard way.
Complete 100% of the journal.
Complete the game without collecting any treasure. No shortcuts.
Reach the City of Gold.
Complete the game.
Obtain the Ankh.
Complete the game without using shortcuts.
Complete the game in under 8 minutes. No shortcuts.
Reach the Temple.
Obtain 500,000 gold.
Rescue 10 or more damsels in one game.
Kill 12 or more shopkeepers in one game.
Win the kapala from Kali.
Reach the Jungle.
Reach the Ice Caves.
Complete 50% of the journal.
Beat the Tutorial.