She wins, she can't really... lose against people she's capable of harming, her superpower is literally being lucky.
So even though Witcher is wayyy more skilled than she is, she'll still win, because the "off chance" she gets a direct hit becomes a "guaranteed" chance. She can take hits yes, but the chances of a horse running Geralt over in the fight are made better then the chance she'll lose due to her luckiness.
If we turn off her "luck" powers, she gets her shit pushed in pretty hard.
Anyway, Domino wins 50/10. Geralts signs will malfunction or misfire. His knee will flare up really bad so he can't walk. He'll get a hand cramp and drop his sword, etc... At the same time Domino is just punishing him if he's still alive and kicking.
The most likely scenario is he slips just as she goes to stab him and he falls face first onto her knife for her.
I see what you tried to do. But you just explained that her powers work fine. A cybernetic, superhuman, telekinetic psychic from the future who claims he could kill anything, couldn't take her out while Deadpool was dealing with a bunch of scrubs. And lucky for her, Deadpool showed up. If there was no PIS in that scene, her tasering his neck would've shorted him out or something but they had to show how badass Cable was. Also bs he took no damage. She hit him with a cattle prod, and gave him quite a few hits. She's just a normal strength woman and he's like I said a superhuman cyborg so he's a lot tougher than her.