No, no, no. This is Batman, remember? With prep-time, Batman can defeat Galactus and Thanos together. That's what I've been told, anyway. Also, Batman's signature archvillian, the Joker, can take over the world anytime he wants, easily, and is able to access 5th-dimension imp powers at will. That's another thing I've learned here.
Yet Batman still beats him easily.
Therefore, I must conclude that Batman could easily defeat Mystique, as well as for that matter all of the X-Men combined.
Now after Batman defeats Mystique by using his Uber-Detective Bat-Sense (tm) to deduce her identity instantly and then KOing her with his left pinky finger while sipping some tea Alfred so kindly has provided, what shall he do next? There's always taking Darkseid down 1v1, but that's kind of beneath him these days, isn't it?
What can Batman do to really CHALLENGE himself, I wonder?