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