12. Michael Fassbender
It would be foolish to expect that every great actor could sustain their highest level of performance for every role that they take on. They're at the whims of the directors and producers behind those projects as well as at the mercy of the material and expecting them to be a conveyor belt of top notch quality is just unrealistic.
Blips in form are to be expected, in other words. Even the most legendary icons of acting had the rare outing that stuck out like a sore thumb, but the key was always that form is temporary and class is permanent. Pretty quickly, they'd usually return to their best.
But what happens when actors you usually expect to be good have a run of poor form that stretches beyond a single movie? What if they make it to the dreaded hat-trick? It might sound a little unlikely, but it's happened to some surprising figures very recently...