Iron Man

There's a version of this saga's beginning that opens with a wormhole or a tesseract or a god falling out of the sky. Instead the actual first spark, in story order, is a billionaire arms manufacturer watching his own missile go off in a crowd he sold it to, and building a very small, very bright thing in his chest so he can keep having opinions about that afterward.

What holds up, watched here as chapter three rather than as the franchise's technical starting point, is how unglamorous the invention itself is: two men in a cave, scrap metal, a car battery, and a problem that has to be solved today or not at all. The suit isn't handed to Tony Stark by circumstance — he builds the ugly version first, badly, twice, before he ever builds the one on the poster.

It's also, in hindsight, the quietest possible entry point for a story about people who will eventually fight gods: everything here is grounded, mortal, solvable with tools you could actually buy. That contrast is worth carrying forward — it's the baseline the rest of the run keeps escalating past.