Here is the full list of all 10 Spoiler Alert achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Watch the credits from finish to start.
Get gold star score in all 10 levels in the Mariachi World.
Uncomplete the main game.
Get gold star score in all 90 main levels.
Find all 3 hidden main treasures.
Unlock all 3 main worlds.
Jump more than 150 times.
Get squished flat as a tortilla.
Do the leap of faith in World 3, level 12 - without middle landing on the support block.
Cause more than 10 time paradoxes.