If the Madrox crowd could be seen from space and we are talking of hundreds of thousands of people, or millions, then there isn't a lot the xmen could do. Even if he had no powers apart from his multiplication at every impact.
IIRC in his debut as a character he beat all of the Fantastic 4, and he can also duplicate anything he holds, give him a gun and minutes later you can have 100.000 people with each with a gun
That is why he has been used as a wespon of mass destruction in many AUs. I don't think Jean or Storm could stop him if he is out of control. The best option is finding the Madrox prime to make the whole multipliying Madrox swarm stop.
In Age of Apocalypse Storm couldnt stop Madrox, and Madrox killed himseld to stop the Madrox clones brainwashed by Apocalypse
Madrox is overpowered in an almost cartoony way, I disagree with the idea that the xmen are having a bad showing against him, I would even say the writers didnt need to give the Madrox dupes superpowers to make him very hard to stop
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