I believe I would slot this at #2, if #1 was Ghost in the Shell (2 movies, 2 series, 1 movie continuing the series and ARISE).
I don't believe there's anything more I need to say about it past that.
The show is aired in an anachronistic order, which is the way it should be watched (the order it aired in, and is numbered by).
The order is:
Mirai Fukuin (2013)
It also has one of the strongest soundracks ever made, not even mentioning Kalafina's songs, which were all a cut above.