I also see Tina mainly at fault here. MC could have tried to imagine what kind of hell would break loose, if instead of stacking he would have fired 10000 of his weak fire lances simultaneously and spread into that town district. Nothing good. On the other hand he only saw what happened to the training target at home, always nothing much, at least nothing to its surrounding. It's Tina's fault, because she never told him. Imaging raising Superman and telling him, "You is super strong, see how you made a dent into this punching bag?" But you are not telling him, that you secretly replaced its materials and that it is now made up of a adamandium woven cloth, filled with neuronium sand and reinforced by 12 Class 10 forcefield-generators shielding it. Then he sees other superheros like Batman, the Flash, Ironfist and Black Canary giving a strong but relative normal made-up punchingbag a good beating. "Oh....Those guy are stronk."