IMO its Kisame
not to take anything away from the Sandaime Raikage but aside from his insanely high chakra levels what I think put him over the top was his body. His body was close enough to being the ultimate defense, nothing but his own attack could even lay asctratch on him...so of course he's gonna be able to take on a biju...a biju couldn't really hurt him. Course he was going to be able to take on 10,000 ninja by himself for 3 days before finally falling...what were they going to be able to do to hurt him? He could have had Shikamaru's chakra levels and done close to the same if he just went off of taijutsu after running out of chakra. not like any attack, even no weapon could even prick him
where as Kisame...Neji with his Byakugan and its ability to see chakra having seen the kyuubi inside Naruto, compared that to a clone of Kisame's that only possed 30% of his chakra...30% of Kisame's chakra also forced Might Guy to unleash the 8th Gate. Guy already was naturally insanely powerful at base. And it helps that Kisame wasn't indestructible making him seem even more powerful...he stood on his biju level chakra alone