In every heroes lifetime, they will defeat, on multiple occasions, a group of villains who will swear to destroy them, and only them, at any cost. These villains are known as a heroes rouges gallery. Batman has the Joker, Penguin, Riddler, and many others. The Flash has Captain Cold, Mirror Master, and Weather Wizard. Then there's aquaman, with Black Manta and Ocean Master (Seriously... the only thing sadder than your only ability being the control of fish, is when those fish go and kick your butt.)
Anyway, for all hero owners, take a moment to consider. For your favorite hero character you control, what villains make up his/her rouges galley. The list can be as long as you want. The villain just has to have sworn himself to the destruction of your hero. At the top of the list, put the rouge whom you feel is your heroes lead rouge.