The Flash and Wonderwoman could take them all out. The Flash alone could take everyone but Piotr. The flash can move at the speed of light, so before any of the X-men could even think about what to do the flash could knock them all out. Piotr would be a problem because he is so tough the Flash can't really hurt him. That is where Wonderwoman comes in.
There is a reason I rank the Flash so high. There is a web site that shows where Wizard ranked the 10 toughest superheroes and the flash kick a good deal of but. It won't let me post the link but just type in
"wizard ranks 10 toughest superheroes" into google and it should be one of the first sites you see