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