Arena-The shores of Kumogakure(where Darui's division fought)
30m apart
I think Kakashi, he used Kamui to take a large explosion to another dimension so I think he can take Oro with Kamui, he can go underground to avoid most of Oro's attacks even the thousand snake tech and Oro's wind techs, he can dodge Kusanagi and even use it to his advantage by chanelling Raikiri into it to numb Orochimaru, his lightning chain is wide enough to chop Manda into pieces and if that doesnt work he can cast genjutsu on Manda like he did with the Root ninjas that were watching Naruto.
30m apart
I think Kakashi, he used Kamui to take a large explosion to another dimension so I think he can take Oro with Kamui, he can go underground to avoid most of Oro's attacks even the thousand snake tech and Oro's wind techs, he can dodge Kusanagi and even use it to his advantage by chanelling Raikiri into it to numb Orochimaru, his lightning chain is wide enough to chop Manda into pieces and if that doesnt work he can cast genjutsu on Manda like he did with the Root ninjas that were watching Naruto.