part 2 is unbeatable however due to a glitch in the game. If you buy it you will never see the ending
Far as I know you just have to beat that battle fast enough, so not unbeatable but it's kind of unintentional difficulty.
I didn't even know about the bug when I played through the game and I got through that part just fine. If you're good at the game it's not even noticeable, just have to defeat a certain boss quickly enough. Hardly 'unbeatable'.
Edit: I should note, though, that there's some optional content where you can battle that same boss over and over and she gets stronger every time in order to unlock...something. Not even sure what, since that part is
pretty much unbeatable. And she's the only boss in the whole game that does this...kind of ridiculous that they missed the bug then. However I'm wasn't under the impression that the locked out stuff was anything major. The big thing is you're missing the chance to challenge this optional boss (well, to challenger her fairly...).