I haven't actually seen Kevin Smith's Cop Out, which, according to BoxOfficeMojo, is his biggest hit, but judging by the trailer and clips I've seen, I'd say it's Kevin Smith's worst and probably the worst film ever made. If you conveniently exclude Red State from his oeuvre, he's in the weird position of his most successful film being his worst and his least successful film, Chasing Amy, being his best. Sure, Clerks and Mallrats made a lot less money in theaters than Chasing Amy, but I think the cult followings that were developed for those two films by the hockey-jersey-and-jorts crowd throughout the '90s eventually made them more popular than Chasing Amy.