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