Natsu, Lucy, Gray, Erza, Wendy, Juvia, Gajeel, Cana, Elfman and Levy have shown ability to level an entire city.
If you're referring to Mirajane giving Makarov the news that Natsu, Gray and Erza destroyed half a city during a mission than it doesn't count. We never saw it, and they clearly can't cause that much destruction all at once, it takes time.
The match i proposed was balanced, both teams have what the other does not. The nin have the speed and power advantage, while the mages have the range advantage.