"Suicide Squad," the latest movie in Warner Bros.' planned slate of DC Comics films, opened last week to even more negative reviews than its widely panned predecessor, "Batman v Superman: Dawn of Justice," deepening doubts about the franchise's long-term viability.

Still, "Suicide Squad" had a big opening weekend and continued to post strong box-office results during the week, as it heads into a crucial second weekend. All eyes will be on how big a dropoff it suffers. For instance, "Batman...