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