“Venom” is, by far, the worst comic book movie franchise out there — the black sheep, er blob, of Marvel and not even a part of the popular Marvel Cinematic Universe. Watching it, unless you’re already a demented diehard fan, is utter agony.Venom, for the blissfully uninitiated, is a symbiotic alien who’s latched onto the body of San Francisco newspaper columnist/schlub Eddie Brock (Tom Hardy), and eats human brains to stay alive.