You guys who say's Oro wins this need to understand that 100% Katsuyu is probably about the size of Mt Myobakuzan. In other words Oro does not have a tecnique large enough destroy, not only a mountain, but a mountain that can break into thousands if not millions of pieces. Add in the poison and well it's overkill.
I know we haven't seen 100% Katsuyu but if you look at the size of the Katsuyu Tsunade and Sakura summoned together with Byakugou released was like what, %5 of it's body? Then you can imagine how big the whole thing is.
I don't see Oro....or any other ninja besides Madara, Jinchuriki (at least 3 or 4 of them together), Jubito, or Hashirama beating that thing.