guys, I'd love to make this a topic. Imho pretty much every attack sequence is reactable. I even think that PK zone-cancels can be reacted to.
The only tool that I think must be guessed is the Kensai 3rd hit (unblockable), which can be cancelled into the armored side attacks or simply be cancelled (slightly later) by pressing the cancel button. This forces a real guess imho.
does any character have something comparable?
the warden vortex somewhat might be, but I don't know. I guess, the valkyre might have some severe mix-ups too, but she relys heavily on hitting her 1st light to start a mixup.