Jennifer Lawrence announced after X-Men Apocalypse she will not return to play Mystique.
In X-Men First Class she gave a decent performance.
In X-Men Days of Future Past, I felt like she phoned in her performance. I prefer hamming it up to behaving as though it is a waste of your time to be acting. Her performance was not only wooden, but it was like she was gobbling valium like Tic Tacs. There was no emotion or infection in her voice. She made almost no facial expressions. For me, the point of going to a movie is paying people to play act. She just wondered around mumbling impassionate phrases.
Hopefully the next actress to play the character emotes better.