The Leader plans to attack the Beast. The Beast knows it's coming. They both have 1 month of prep. They both have a reasonable amount of information about the other's capabilities.
Neither gets to use any flunkies or friends--it's strictly those two individuals, and whatever tech they create. They are allowed to make robot flunkies.
The eventual battle will take place at the X-Mansion. Beast has all the tech that's normally there at his disposal, plus whatever else he could reasonably build. EDIT: No time machine though!!! The Leader gets to use whatever kinds of tech he normally manages to use.
In character. Win by any means.
Who wins and why?