Keeping the balance. Its as important as fighting for good. If the good guys are winning too easily, they'll be defeated when the next big bad shows up. If the bad guys are winning too easily, well... that's kind of bad in its own right. So whichever side is currently in the lead, I'll be messing with. Should be fun pretending to be evil every once in a while too.
if I had super powers I'd se them to protect the weak right the wrongs and bring the bad guys and gals to justice 'cause I'd fight for freedom,truth,honor and justice keeping my dual idenities a secret.