The Mighty is the story of two seriously handicapped teenage boys. Kevin's medical condition has twisted his body and stunted his growth. He calls himself Freak, not out of self loathing but as a dare to those who see him as a freak. Max has a large solid body but his mind is slow because of his fears and the shadows of ugly memories. The belief that he is just like his father, Killer Kain.
Some people can be real rough on others who are different.
This is especially true of adolescents. Those that don't fit in end up being the target for a lot of abuse from their peers. Both Kevin and Max are on the outside, one as a big target for kids who get their kicks from tormenting him because he will not defend himself, the other a bent oddity who, not only takes insults in stride, but mocks the insulters for their lack of imagination. From this description one could get the impression that The Mighty is a depressing, angry movie. It is not.