I want a girl in a wonder woman costume to beat me up
Why would you specifically need for her to dress like Wonder Woman?
I want to know what it feels to be powerless
Getting beat up is not a healthy sexual fantasy. It may mean you have a mental issue and I would recommend that you should go and get checked out.
Nah, I just think it would be cool.
What is cool is trying to date a woman that is strong and powerful, but it is not cool for you to wish that they would beat you up as it wouldn't be healthy for your relationship. I still strongly suggest that you find someone to help you with your sexual fantasy and how it can be less violent.