In the world of Marvel Comics, and X-Men comics in particular, some heroes and villains have always been true to their path of good or evil. Others, however, have displayed a more flexible sense of morality, or have grown and changed according to their experiences. Throughout their existence, the X-Men have always given villains a chance to do better.
Source：https://www.cbr.com/xmen-villains-join-team-order/
