“Human beings are strong because we have the ability to change ourselves.” Saitama, One Punch Man
The idea of stopping a meteor headed towards our planet with nothing but a superpowered human being sounds like a physical impossibility. But if you had a powerful enough, strong enough, fast enough human, it could be done, so long as you obeyed the laws of physics and conserved energy and momentum.
The speed your human would need to hit the meteor with would be tremendous; there would need to be something special about this human’s atoms to keep them from flying apart; the energy released by the in-air explosion would be catastrophically huge. But it could, in fact, save the city — or the entire planet — that it would have completely annihilated otherwise.