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 10 or more damsels in one game.
Complete the game.
Complete the game without using shortcuts.
Kill 12 or more shopkeepers in one game.
Reach the City of Gold.
Reach the Temple.
Obtain the Ankh.
Win the kapala from Kali.
Complete 50% of the journal.
Reach the Ice Caves.
Beat the Tutorial.
Reach the Jungle.
Obtain 500,000 gold.
Complete the game in under 8 minutes. No shortcuts.
Play Adventure Mode 1000 times.
Complete the game the hard way.
Complete 100% of the journal.
Complete the game without collecting any treasure. No shortcuts.
Complete the game with at least two players alive. No shortcuts.
Rescue all 16 hidden characters.