Who is it?
In your opinion, which hero would be most likely to effectively operate in our world? Which would be most likely to exist in our world? I suggest choosing a street-level hero, as they're usually more realistic, but if you can make a case for Thor or Quasar or any other powerful hero, be my guest.
How do you think whichever hero you have chosen would operate? What about their methods or equipment would need adapting to fit in with our world?
Feel free to include DC characters as well as Marvel, if you like.
For a bonus, which villains would fit the question as well?
Go into as much detail as you want, and, most importantly...