Karate, kung fu, judo - the list goes on and on with many that I’ve never even heard of before. Which is the deadliest, using only the hands, feet (and perhaps the head)? No weapons!
My judo instructor always said that it usually comes down to who gets the first good blow in. He was a coach for the men’s olympic team at one point, so his opinion has some merit.
Most advanced martial artists have a way or three to kill you very quickly if they can act first. It allcomes down to who moves first and who gets a little lucky.
It’s probably the art of convincing people that condoms are immoral. The masters of that art kill thousands every year.
In my experience, there isn’t too much to supposed “death” techniques. People are really pretty tough to kill - especially a resisting opponent. Truly “vital” targets can be pretty hard to identify and get at.
There are a couple of basic ways to break someone’s neck - with countless permutations. But you have to work to get into position to pull them off. Not anything I have encountered being taught too much. Wouldn’t be all that big a market for it IMO. I’d suggest more people need to know how to wrap up drunken Uncle Leo at a family gathering, than snapping his neck.
I’d suspect judo-type throws onto hard surfaces would probably have as much chance of quickly maiming/killing an opponent as anything.
I also don’t know of any art that intentionally concentrates on killing - which is not much more useful than incapacitation, and bears considerably greater legal implications.
In a few short months of Tai Kwon Do I have learned a couple of ways to kill. And snap joints. Fun stuff. And easy. I am sure each form has these moves. Kind of an apples and oranges thing.
Can I nominate this as “Biggest Stretch to Make a Political Point in a Non-Political Thread”?
No, you’ll have to start a new thread in the BBQ Pit for that, I’m afraid. 
Deja Fu is still the deadliest.
I nominate the ancient Lancastrian martial art of “ecky thump”, involving violence with black puddings.
How lethal is Aikido? That might be good because it’s not so much offense oriented as defense. So it might be better at blocking off the first shot and countering with a death blow.
Dinsdale - I taught Karate for some time and despite knowing numerous (unarmed ways) in which to cause serious injury and even death, I would never pass this information on to any student due to ethical considerations.
I agree that disabling an opponent is sufficient as you are then free from attack and have the option to escape. I cannot imagine where I would have to go to the point of killing anyone if I was defending myself.
The advantage in any fight goes to the one who gets the first strike and my own experience has shown me that one strike is sometimes all you need if it’s done well.
Qadgop - Eckythump (it’s actually one word) is indeed awe inspiring but I had heard that the art had been lost for centuries. How is it that you come by this arcane knowledge?
I can tell you that the deadliest and **most brutal ** martial art is llap goch!!!
You can tell I’m serious because I use lots of bolding and italics.
Seriously, I think Feynn has the right track. There is no one “most deadly” art. As with most things, it’s the skill of the artist and what they are willing to do.
And, to get in the debate, I like Kuk Sool Won so much I’m going to be driving almost 7 miles to go to class starting in January.
No, it’s two words. It’s so deadly that it once killed a man, and he didn’t mind it.
I just remembered…didn’t the Russians invent a special martial art for their military personnel that is supposedly the most efficient killing art in history? I don’t remember the name of it.
The Russian military martial art is known as SAMBO. And it is a highly effective hand-to-hand combat style. But its not really about killing, just effective practical defense/offense.
The absolute “deadliest” forms are the grappling techniques. So, sorry to those Karate and Tae Kwon Do afficianados, but your chopsocky is useless in practical situations. My cite is witnessing numerous mixed-martial art full-contact tournaments where stand-up practitioners (karate, TKD, Boxing etc) consistently find themselves having their ass handed to them.
In Jiujistu, Hapkido, Aikido (all variations on the same basic principles (Jiujitsu and Aikido are Japanese, Hapkido is Korean)) there are countless very simple manuevers whereby you can break and shatter bones or suffocate your opponent in various ways.
But there are many many styles that all do those same things, only in different ways. Any sufficiently trained Tae Kwon Do practitioner could kill with a powerful kick to the temple or throat (given the chance).
The question is more which style is the most effective in allowing you successfully to use a specific technique, rather than which is deadliest, since they all can be. Except Karate, which sucks.
Eidolon - "So, sorry to those Karate and Tae Kwon Do afficianados, but your chopsocky is useless in practical situations. My cite is witnessing numerous mixed-martial art full-contact tournaments where stand-up practitioners (karate, TKD, Boxing etc) consistently find themselves having their ass handed to them.
"
Please define practical situation?
There is a huge difference from the formal structured movements (like kata) and real time, real world ass kicking. There are usually no referees or anyone keeping track of points. The only point in practical situations is getting out intact.
So… here’s some examples of practical situations I’ve experienced. I’ll exclude the numerpus fights with drunks because they never knew what hit them.
Would that be where you get jumped by two guys just because they think beating the crap out of you is a fun thing to do? Seeing your buddy quickly rendered into a quivering mass on the ground seems to be a strong deterrent.
Would that be when you step out from the pub into the middle of a small gang war and end up fighting three assailants? The results of this were: #1. unconcious, #2. crippled, and #3. who wisely reconsidered trying to take me out? Granted… they were punks and had more guts than skill.
Knowing that limiting yourself to one style makes one vulnerable
I studied other forms over the years. We had a significant group that got together regularly to share and teach different forms and skills. I have no issue with anyone who wants to play in the dirt and know there are a few practitioners of Judo and Ju Jitsu who can level you with various striking techniques.
I’m really from the “whatever works” school and not a big fan of rigid forms. Call my style, Feynn Fu… perhaps the deadliest art ever. 
I agree that when fights occur between two highly trained individuals the person who has the best ground fighting technique (combined with excellent defensive skills) is likely to win if they can get their opponent to the ground. If you are unable to get your opponent to the ground you had better have some good stand up skills too or you’re the one who will have their ass handed to them.
It’s all about balance and knowing never to mess with an Aikido master by entering their space. Trust me on this one.
I’ve heard good things about that form from Indonesia. I believe it’s called silat. It’s apparently good for when you just care about getting out of there and don’t spar for points.
I have had fun sparring with numerous karatekas. To generalize, there is a stage in their development where they gain sufficient experience in sparring such that they cease being predictable. Also, as feynn says, many karatekas - as well as most accomplished martial artists I know - have studied various arts. Finally, there are so many styles of karate, that it is almost meaningless to refer to it as a singluar style.
If you want lethality, get a carry permit.
Well you defined practical situation fairly well. And I’m glad your training came in useful. But you’ve also stated you’ve done some cross-training. So stand-up techniques are not completely useless, a well placed strike is a well placed strike. But the minute your assailant closes range or grapples you’re in deep trouble, especially if there is a significant weight/strength/height difference.
Have you ever watched Ultimate Fighting or the associated style tournaments? This is 1v1 asskicking. There are no referees, no points and no rules. (well, ok, there USED to be no rules, but there are very few rules). Stand-up fighters don’t even bother entering anymore. And like you said, the best fighers in this field are those that are cross-trainers, that is, they’ve studied a variety of techniques and have achieved an awesome balance of stand-up and striking techniques.
Of course, there are situations where sheer size and brutality win out over technique. Tank Abbot won many matches at UFC and he was a self-professed “street fighter”. No technique… just size and muscle.
And in closing, have you ever watched Olympic Tae Kwon Do? They do more holding of each other than kicking… at which point I would toss them to the ground and rain blows mericlessly upon their head…