It depends, of course, on what kind of comparison/contrast you are doing (i.e., comparing characters, situations, etc.). But the basic idea of a hook is to propose something relateable for a reader that can be more general than the specifics of your paper. So with Antigone, you want to think of the larger themes: the strength of the individual over her tie to the community, the tragic willingness to die for what one believes, or maybe the strength of the outsider. Using one of these, a good hook could potentially be something like, "Perhaps it is not always a terrible thing, to be willing to die." Then your intro would progress forwards into a contrast between Antigone and Ismene. It could also be, "Too often in political systems, the bravest one is she who refuses to listen." Whatever theme will guide your compare/contrast, broaden it into a general statement and then you'll have an engaging way into your intro paragraph.