This is AvX Magneto.
Original Mugen 1.0 only file:
http://www.infinitymugenteam.com/Forum_345/index.php?topic=41467.0
Stage also available there if you want it, it works with WinMugen.
Now for Magneto himself.
Patch files for WinMugen:
http://www.mediafire.com/?1zk17h8a7o1qqwb
Enjoy~