The X-Men have become known for bringing villains into their ranks. Sometimes, this has worked out very well, like with Rogue; other times, it's been disastrous. Often, X-Men villains have been victims of human racism, which the members of the X-Men understand all too well. That sympathy has caused the X-Men to go too easy on their enemies, allowing the villains to take advantage of them.
Source：https://www.cbr.com/marvel-villains-xmen-went-too-easy-on/
