Tsunade charges at Kakashi, given it's her only method of combat. Kakashi backs up, causing her punch to miss, and her hitting the ground sends rubble and dust into the air. Kakashi uses the obstruction of line of sight to hide underground and send a Raiton Clone out in his place. Raiton Clone engages Tsunade for a while, then kamikazes itself and paralyzes her. Kakashi seizes the opportunity, emerging from underground with a readied Raikiri and bisects her, then pierces her skull several times for good measure thanks to full knowledge on Byakugo.
If she brings out Katsuyu, Kakashi can simply Doton and re-emerge with a readied Raiden to chop through the slug before it can split into smaller slugs. Or, he can camp underground and wait out the summon timing.
Kakashi can obstruct line of sight himself as well with Doton / Suiton walls and smoke bombs. He can also use Suitons to push her back to avoid CQC. He can also use Raikiri Wolf to paralyze her from a distance. Kakashi has options, something Tsunade doesn't have and why I believe she loses this.