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