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