This is a silly idea that might just work really well.
Everyone is a “normal person” who is trying to become a superhero. They do this by purposely putting themselves into dangerous situations: radioactive waste, radioactive spiders, accidents with magic, etcetera.
The goal is to get into those situations, but also to not die. That’s when you turn into a superhero and win.
Extra Idea: players start with a “secret identity” that dictates the rules around what kind of superhero they can become, and what skills they already have. This differentiates players more and puts them on different paths.
Extra Idea: the game doesn’t end once a player becomes a superhero, they also have to do one “heroic act”. (Which allows another player to become a superhero + beat them to the punch and win the game.)