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