Tsunade seemed strong and all, and then two chapters later she's owned by Kabuto.
Kabuto did abuse her bloodphobia. I can't really remember, but Tsunade clearly had the upper hand in that fight, right? With Kabuto even mentioning along 'If she hits me I'm dead, blablabla' the same line that everyone pulls off every time somebody gets stronger.
But it was a while since I watched that fight, so yeah..