Among the ongoing anime series, my AP instincts tell me that "
Captain Earth"
might have one in the near-end episodes. Currently in the series, they are
showing us that the leader of the villians is a little girl named "
Setsuna". This
means she will probably end up as the final boss of the series. If this is so, I
can imagine a scenario where she absorbs the power of all the minions, who
will likely be all dead by the end, or reveal her true power and transform into
a mature form. I say this because I've rarely seen an anime series putting a
little girl as a final boss against a male protagonist in fantasy genre.
I suspect that this is usually because a male protagonist fighting a little girl
as the final boss reduces the seriousness for the climax of the series.
Just a theory though.