Now that you mention it....  I think the best thing to do next, would be 
to have the MK outclassed by the most powerful Magical Girl there is.  
She's so powerful, she isn't a Magical Girl....  The one, the only....

LINA INVERSE!!!!!!

While Lina-sama is very powerful, (Lina's note:Thank you) she isn't
the most powerful 'magical girl' there is. After all, while Lina blows up
cities (or, at least, large villages) Sailor Saturn blows up whole 
planets. 

Still, Lina is very powerful, and extremely skilled (she can pull of the
Dragon Slave just like that, no stock footage, no posing, no silly gestures.
^_^)
and would probably beat most magical girls.
Actually, I have been thinking of using her as a villian in a fic. Just take
a bit of time/dimension travel, one plot point from Slayers NEXT, alter a
little,
and you have a great villian for the Senshi. ^_^

Well, this is my opinion, anyway, but I'm more than a little biased. ^_^
-----------
The Martian.
Jussi.Nikander@alien.nixu.fi
-----------
Compared to this ice cream the human lifespan is just
the blink of an eye.
	-Jean in episode 19 of Nadia