Here is the full list of all 20 Spelunky achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
Complete 50% of the journal.
Reach the Ice Caves.
Reach the Jungle.
Beat the Tutorial.
Reach the Temple.
Complete the game.
Obtain 500,000 gold.
Reach the City of Gold.
Obtain the Ankh.
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.
Win the kapala from Kali.
Rescue all 16 hidden characters.