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