lolz thats tru.Most likely Konan
Why:.Deidara might get desperate ( once again -_-) and be a suicide bomber in which Konan would win ( she could just fly away).
OR
Deidara could burn the paper Konan uses with his explosions ( maybe?)
if she is toooooooooooooooooooooooooooooooooo well prepaired...she can takeout everyone excluding these with izanagithats true
Konan may win
He didn't make everyone seem fairly equal because Pein took out Kakashi quick and easy but then Naruto came and thrashed Pein of course Naruto never did technically win that fight since Pein turned good before it ended but still he didn't dei quick and easy like Kakashi so...and thats just one example out of the Naruto universe.Popular logic.....Who knows If Deidara planned a long time ahead and knew Madara's weakness he might have gave Madara a run for his money with his bombs too.
That's the beauty of Kishi he made everyone seem fairly equal.