There aren't too many people out there who don't like Denzel Washington. In my opinion, the worst thing you can say about him is that he takes on too many similar roles (which is a moot point, since he's usually awesome in them).
However, while the actor's powerful performances have earned him five Academy Award nominations, not all of Washington's work has been well-received by critics. This is especially true for the film John Q. Though it was a box office success and a huge hit with regular audiences, the film was poorly received by critics who believed that the film forced its agenda in an awkward and overbearing manner.
Frankly, of all the films on this list, John Q feels the most out of place. While the critics have a point about the movie's lack of subtlety, the film is undeniably affecting and Washington is excellent in the role. If John Q is considered one of Denzel Washington's worst movies, then the two-time Oscar winner is doing fine.