So you want to win the swordfight! Some brainstorming on how that might go down while avoiding a mutual kill or delayed mutual kill.
Physical impossibility: The gold standard, and what you always strive for. You get your shot in while simultaneously blocking their line of attack/controlling their weapon/moving off the line and past so that, even if they were uninjured and fully aware, they could not hit you. Strive for this. Difficult to achieve.
Finish the technique: I've heard the Atienza guys separate their material into three phases. Phase 1 is entry, Phase 2 is the main striking phase, Phase 3 is takedowns/disarms/joint locks/finishers. If you're sparring, you typically are only working on Phase 1 material. Phase 1 is extremely difficult and multifaceted- the sport of fencing is basically just phase 1 material.
From my fencing skills, I am extremely comfortable with a first blood kind of fight, but when I started doing FMA, I was shocked at how it felt while doing some sparring kind of stuff when I would cut someone and they would then grab my wrist, pull me in, and keep fighting. I would blank. Aikido is mostly phase 3 material- extremely difficult to pull off in a sparring context. A lot of the critique for disarms and finishes is that they are complicated or showy- "you'd never be able to pull that off in a real fight." with the basis of comparison to a fully active sparring partner. And it's true, it's very hard. but that's not where that material really shines.
What that's really about is phase 3- you've already dealt serious or possibly fatal injury to your opponent, and you need to make sure they don't get you during the 10-30 seconds that they're dying. Then all the material becomes a lot easier to perform, so much so that you may get the opposite response from the critics- "you killed them like 20 minutes ago, why are you still doing that, this is not self-defense, oh the humanity." All true. From a battlefield perspective, however, you sliced this guy good, he's going to die in 15 seconds, but his buddy is going to be here in 5 so I really need him to die right now so I can deal with this new situation. Or, from another perspective, you've emptied his guts on the ground and he's going to die, but you're not doing him any favors by prolonging the experience.
In any case, to get out of a sword fight, phase 3 material offers options if you can apply it in a timely manner. I've been making a point to tag it on to any sparring I do, even if it's only in my head.
Trade: Accepting a minor wound in return for a major one. A lot of the good tech for the gold standard of not getting touched will have this its failure states. That is, you make your attack and get off the line, and if you don't make it instead of getting a sword in the head you get it glancing off the shoulder. In sparring with competitive types it may help to keep separate tabs in your head. "Under these rules, a torso hit is fatal. However, my shot was solid into the heart while his glanced off my shoulder blade, that's a reasonable trade."
Grievous bodily harm: Your attack does so much biomechanical damage that they are not physically able to respond. A lot of two-handed weapon stuff has this aspect to it, while knife material goes after the same effect through multiple hits. Maybe unreliable to depend on in one blow, especially with any degree of armor involved, but you'll get there eventually if you keep at it.
So they've got their dead man's ten (or more) seconds. These outcomes are about why they decide not to attack with the time they have left. In other words, some reasons opponents decide to give up.
Fresh fight: You've hit them, and put together enough of a semblance of being complete unphased and ready for more that the prospect of starting all over again, now with an injury, is just too much for them to contemplate. Related in performance to Physical Impossibility, but more about appearance than actual fact. Just as being ready but not appearing to be ready can draw a reckless and easily countered attack, appearing ready even if you're not can dissuade one from trying.
Technical mastery or Winning by the Rules: By whatever standards your opponent has, you have so clearly won that they stop fighting. I read a blog somewhere where someone discussed how it seemed that police officers would get shot and sit down, out of the fight, regardless of the wound severity, where criminals would get shot in the heart and just keep on going. He theorized that police officers are rule-following types, and childhood cops'n'robbers rules said if you got shot, well, you lost. Whereas criminals are not into acknowledging rules. Could be this sort of thing, or ingrained sparring habits. Free bonus if you trigger them in other people (never hurts to try tapping out to get someone to release a hold even when they shouldn't), be careful to avoid engraving them in your own training.
Devastation: the mental equivalent of grevious bodily harm. There's so much blood, or pain, or so many wounds, that the opponent thinks they cannot function, even if they can.
Puzzlement: very good thing to cause. If your opponent is trying to figure out what just happened and how they got hit, they're not fighting, and they're not thinking about what else they could do. Tricks and misdirection can cause this ("I blocked that strike, I'm still blocking it, why am I bleeding?" "Because you didn't block the knife I drew while I was swinging that sword"), but so can moves from totally different styles, or an unexpected strong/skilled response from an underestimated opponent. Related: if an opponent thinks you just got lucky, it is to your benefit to let them keep that belief.
Stunning blow: Could be a physiological stunning effect, but could also be a sort "boing!" effect from something getting totally stuffed. A stop-thrust that physically stops the arm, a body bash that stops movement or knocks them back. Whatever they were doing got interrupted, and they have to drop the rest of the plan and start something new. Akin to puzzlement.
Preconditioning: I was always dubious about the tactical benefits of fear or intimidation. Banging on your shield or war cries or whatever. It could make people not want to fight, maybe, but if they've managed to stand their ground, it's not like they're just going to open up and let you hit them. However, thinking about this stuff made me consider a different possibility: fear and intimidation help make people give up when you kill them. In a large-scale battle any effort to nudge the scales away from people fighting all the way through their dead man's ten would be a serious advantage. Thus while I remain dubious about the value of trying to strike fear in the heart of the opponents in any sort of competition setting, it definitely has its place.
And Stay Down: sort of a combination of Fresh Fight and Stunning Blow. They get hit, they pause, regroup, start to move again... and you hit 'em again right at the start. Has psychological power far beyond whatever the physical effect would warrant.
Flurry: Hitting someone many times, even if most hits are not very damaging, and even beyond the OODA loop interruption consequences, has a strong psychologic effect. "My defenses are useless, I can't do anything." Counting wounds or doing internal damage assessment is every bit as good as puzzlement.
And few additional easy ways to lose after you've won:
Don't know they're dead: If you land a very successful attack- surprising and fast- your opponent didn't see it coming. They may not have seen it at all. In a fighting state, they may not have FELT it at all. Even though they're dying. So they don't stop fighting or slow down or change what they're doing one bit. Dangerous! Thus, it's important to stay ready and keep fighting. Related: In a similar manner it's often difficult to asses how hard something hits from an outside perspective. Hits that seem to cause a big reaction usually do so because the opponent was starting to react (move away or cover) BEFORE they got hit. Totally surprising hits, which usually land much harder, cause no immediate reaction.
Did I get 'em? You hit, and then stop and look to see the effect your attack had. The downfall of every would be hero or heroine in horror movies, where they stab the killer in the back and then watch instead of fighting more. It's not safe to stop fighting even if you did get 'em.
Got 'em: You hit, know that you got them, and stop fighting. It's not safe to stop fighting even if you did get 'em.