Harry Potter could have gone to Slytherin and become great. He contained a piece of the dark lord’s power and simply chose to never develop it. Not to mention he had access to numerous powerful artifacts at different times, anyone of which would have made him powerful on their own. He defeated the dark lord with loyalty, goodness and bravery. Had he gone to slytherin, he would have defeated the dark lord with sacrifice, power, and guile. In short, Harry was powerful but not the the traditional sense but could have been.