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