In a fight of feats Orochimaru has this 1v1
Tsunade has:
Super strength taijustu
summoning
regeneration
THE ONLY THING TSUNADE HAS OVER OROCHIMARU IS IN TAIJUST/ RAW STRENGTH
This is why-
Manda + eight branches beats whatever percentage of Katsyua tsunade can conjure
Orochimaru has better regeneration than Tsunade
So, just considering their base abilities, in order to believe that Tsunade wins in a 1v1 you have to accept that her strength is enough to take out Orochimaru- the worst part is that even if she does somehow punch Orochimaru to bits, I highly doubt she could do anything to his true form. I say she gets paralyzed and dies.
Now thats just using the feats that each character has, if we go by hype Orochimaru slaughters
He was able to control Tobirama -( the same tobirama that killed Izuna who faught and trained with Madara)
He has senju DNA and considering that he took over zetsu's body he should have all of his abilties,
Not only is that true, but he absorbed all of Kabuto's memories so its possible that he can now use Dragon sage mode, and some of Kabuto's techniques like muki tensei.
With feats: Orochimaru in base is a good match for tsunade, but when he goes into his true form Tsunade is getting wrecked.
With hype: Orochimaru slaughters low diff.