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