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