One of my favourite movie tropes is the "Unlikely Hero"*. He's got no superhero qualifications. And yet, when the chips are down, through moxie, guile, or just plain luck, he manages to save the world. Think Peter Parker (Spiderman), Sam Whitwicky (Transformers), or Neo (The Matrix).
The Right Place at The Right Time
Help from Friends
Unlikely Heroes can acheive great things - often things they'd never have though possible - but sooner or later they come up against their own limitations. When that happens, there's only one way forward.. A Montage!
Through the art of the montage, the Unlikely Hero learns the skills he needs to fulfill his destiny.
The real test of a hero is simple: Does the studio commission a sequel?
* Movie trope enthusiasts will notice that I'm really describing the Action Survivor. I decided that wasn't a catchy title.
** If you ignore some of the low-market-share platforms, there are few other options, but most involve a fair amount of glue code