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