Suggested by JHG195 Dudley Dursley used to be a rather mean cousin to Harry Potter but gradually became a nicer guy. He never learned any magical abilities and isn’t much of a fighter, but he does have experience on his side. Kiki is only 13 and while she is good at riding on a broom, she never learned how to properly fight. In this case the age difference is very difficult to overcome and I don’t think her attacks would have enough weight behind them. Dudley Dursley wins.