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