Boys would tell you in gory detail how they'd draw and quarter and do all sorts of horrendous things to finish him off. Transformation is big. You also see it in toys that are designed to transform from one kind of vehicle into another. For boys, however, the transformation is generally from less powerful into more powerful. Girls want to become more glamorous and magical.
Kids also have a lot of fears that come from being small in a world of large and powerful things.
They fear the breakup of the family, and they fear toxicity. They fear bigger kids, and they fear the dark or the unknown. Really successful antagonists typically bundle together a number of these fears such as size, power, and toxicity. These fears are manifested more in linear entertainment than they are in interactive. Larger and larger amounts of information are being sent in smaller and smaller time frames.