A martial artist who encountered knives enough would simply be dead
An amateur with a knife can still kill a martial artist, the MC is so inexperienced that this current enemy is extremely dangerous. A trained expert with weapons would annihilate him and is more of a late game enemy tbh
Honestly that's cap, you can encounter a guy with a knife a lot of times and still survive, the key strategy is turning into a track-star, that or you're insanely lucky/have a weapon of your own
However with the amateur knife attacker you're right 50% of the time, in most cases a guy with a knife is always going to be the biggest threat in the room, even if someone does Martial Arts, the other 50% the guy fails a swipe, gets his arm pinned and he can't use the knife anymore. Seen a former MMA fighter on twitter perfectly restrain a guy with a knife, I've never really seen a video or seen any news articles about a trained fighter losing/dying to a knife encounter yet.
There's a channel that simulates knife encounters with different fighters using different martial arts, and personally I believe it definitely gave me ideas on how to improve on my own martial arts, especially against dangerous encounters like with a knife if there's no option to run. The last dude who was a former UFC fighter deadass looked like Leon Kennedy in all 3 rounds he fought the knife attacker.
I highly suggest anyone who's interested in knife defense to take a good look at this, it's really, really humbling but at the same time highly informative. Something that I personally noticed is that whenever you try grappling with someone with a knife you're usually just a dead-man at that point, especially if they're in the advantageous position, but the fighters who chose to stand-up and strike, usually throwing kick combinations and punches are the ones who would've "survived" the simulation.
My bad for going on a tangent, I still think no one should ever have to fight someone with a knife, the best case-scenario is that you bought yourself a concealed-carry, and that's that, a gun would always beat a knife. If you don't like in America, you at least have a taser, pepper spray, or anything you have on you, never try fighting someone who has a knife if you can absolutely avoid it.
(since the video I was referring to has a broken link, anyone who wanted to watch it it's called "8 Martial Artists locked with a Knife Attacker". USDC by Rokas Leo