Lol she didn't really have a bad battle against Orochimaru. She was afraid of blood, so she was petrified. After she received two mortal strikes and a beating, she got over her fear, healed herself to full, and preceded to **** up kabuto and just whoop on orochimaru. She wielded a 6story building-size sword like it was a kumai, striking Manda(the biggest summon who was fast enough to outmaneuver Gamabunta and Jiraiya, and was known by all for being a bad ass). - Tsunade in one single blow took out Manda. Then she beat on Orochimaru until he was forced to flee in which case she was still standing right to fight more.
That's a bad battle? We haven't really seen her fight in the anime in anything else really so... kinda dumb statement..
Also, it takes a LOT more chakra to heal somebody, so her healing the hundreds or thousands of people in Konaha after summoning her slugs and spreading it all out through the slugs, THEN she again was still ready to fight.. kinda better than a hokage who would have just fought and probably died until Naruto arrived saving absolutely nobody..
