Honestly, I was fully expecting him to dodge that sword swing or even mitigate how hard it hit him through a partial dodge. Were the 'victim' someone who didn't have strong skin it would've cleaved straight through their body. That said, I specifically made the sword huge and heavy so that even the blunt force it projects would shatter bones or cause injury even if it didn't cut, so there's that.
I should probably point as well that Shax won't just stop the fight on a whim and walk away. She lives and breathes fighting. She'd happily take on something that has proven itself to be more powerful than her with a grin on her face, because it's not just a challenge, it's fun. She fights to the death, so either one of them dies, or one of them flees, and the one who flees isn't gonna be Shax. (I suppose something else could interrupt in some way too, but it would take a LOT for her to even consider dropping the fight.)