Break them. Their arms. Their legs. Their hands. Whatever else they’re using that you don’t want them to use, like their jaw to keep them from talking. Their spine. Paralyze them.
It will probably do more permanent damage and will be difficult to move them if you have to, but you can cripple them for life.
That is an option.
The guy with the fractured or snapped knee cannot chase you. The guy with the broken jaw can’t yell for his buddies. They may be able to swing their arm, but they can’t use it if it’s broken. You damage them to the point where they are no longer capable of fighting back.
Or… drug them.
However, this isn’t as simple as it sounds. Drugs affect people in different ways, the amount you need is based on their height, their weight, their body, and their susceptibility to it in the first place which is very difficult to judge if you don’t have access to their medical history. You gas a room and even if it takes out like 90% of them, you still have to stay alert for that 10% where it didn’t quite take.
Drugs are the other cheat which end up in fiction a lot as the easy way out. They don’t work as advertised. They are not any more consistent than anything else. It’s a situation where the amount you need to put one of the guys to sleep is just going to flat out kill the one next to him. There is no one size fits all dosage.
And you have to keep dosing them consistently at regular intervals or it will wear off. You have to come back and check to make sure they didn’t come to. And you should probably tie them up anyway, just in case.
Just to be clear, your choices are:
Cripple them for life.
Tie them up.
Find a way to deescalate the situation.
Using your own body as the lock up point like in a hold or a throw or just sitting on them still counts as tying them up. The downside to that is you have to keep holding onto them or let them go. This is why breaking them is better if you need to exit a situation because they cannot pursue.
Lastly: superpowers. (Which will technically count toward “tying them up” 9/10.)
Introducing fantasy elements will change the game some, but doesn’t change the fact that a violent altercation between two people or more is about deciding “me or them”.
Any mook your character leaves alive is one that can come back at them later, even if they’ve tied them up. They can pass on information about them to their friends. They can holler for the guards. They can come after you while your back is turned because you thought they were incapacitated, but they really weren’t or only passed out for three seconds. Or your characters will run into them again later with more of their friends. Thought two mooks were bad? Try eight? Try fourteen and they turned on the gun turrets.
Depending on what they have access to they can really ruin your day.
It’s an interesting character choice.
Do they leave these guys alive knowing that they can screw them over later? Are they in a position where they can afford that possibility? What are their feelings on this subject? How does that conflict with other characters in the narrative?
This is the problem. Your characters choices actually have consequences outside of the fight, outside of their relationship with these very specific characters. While that can go on to become “a moral lesson” about the importance of kindness and pacifism, it can easy go the other direction.
Which is the chance you take.
Media tries to use the K.O. as a substitute for death. There is no substitute for death. Only dead men tell no tales. (And even then, they still do. It just takes longer.)
Fighting to subdue takes longer and it is more difficult that fighting to kill.
There is actually nothing more efficient in a fight than killing.
The question is not what is “most efficient”. It’s is killing really the best solution to this problem? Is it something your character or characters can stomach? Where do they draw the line? Is there a line? Does it line up with their goal?
Death can be just as detrimental to the overall goal as leaving the mook tied up.
You live in the uncertainty of the right choice. All your characters can do is make choices in accordance with what they believe and then live with the consequences. There will always be consequences. However, the question is: did they achieve their goals along the way?
Once your character chooses to engage in violent action, they are closing off alternate options and are signing up for not only the possibility of death but the likelihood. Violence is about hurting people, once your character chooses to engage then they’ve moved away from the options that lead to no one getting hurt or the vast majority of people surviving. If you don’t want to hurt anyone, then don’t fight. Really. There are always other options, even in your fiction and they are actually worth considering. The presentation that death is the worst thing that can happen to someone in regards to violence and that anything else that happens, so long as they remain alive, is… really screwed up, frankly.
Remember, knee capping some poor asshole is crueler than just flat out killing them. There are a lot of ways to inflict violence on someone that actually makes death the kinder option.
Plus, violence often creates as many problems as it solves.
Avoidance and death are both more efficient than subdual. Even if you incapacitate someone with a taser, you still have to tie them up.
That’s the problem.
They will become a problem. You have to eventually let them go. Or someone else will. (Or kill them.)