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.
Reach the Temple.
Obtain the Ankh.
Kill 12 or more shopkeepers in one game.
Win the kapala from Kali.
Complete 50% of the journal.
Reach the Ice Caves.
Reach the Jungle.
Beat the Tutorial.
Complete the game.
Obtain 500,000 gold.
Reach the City of Gold.
Complete the game without using shortcuts.
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.