Here is the full list of all 20 Spelunky achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
Rescue all 16 hidden characters.
Complete 100% of the journal.
Complete the game the hard way.
Obtain 500,000 gold.
Reach the City of Gold.
Rescue 10 or more damsels in one game.
Kill 12 or more shopkeepers in one game.
Complete the game.
Complete the game without using shortcuts.
Reach the Temple.
Win the kapala from Kali.
Obtain the Ankh.
Complete 50% of the journal.
Beat the Tutorial.
Reach the Ice Caves.
Reach the Jungle.
Complete the game in under 8 minutes. No shortcuts.
Play Adventure Mode 1000 times.
Complete the game without collecting any treasure. No shortcuts.
Complete the game with at least two players alive. No shortcuts.