On face value, nothing. You should be kept completely away from anything close to it, if your aim is as stated. But frankly, I don't think you have even begun to think about what you've actually asked… and is full of simple movie-influenced delusion and fantasy.
Ha, every time…
Not in Australia.
You asked a frankly ludicrous question, phrased it as fantasy warrior as you could, and you're surprised by the responses? Dude. Grow up.
I wouldn't. At all. It's the last thing I'd direct them to, as it's simply not a "cure" in the slightest… in fact, one line of thought has it that martial arts are more of an amplifier than anything else… good becomes better, bad becomes worse… so no, it's the last thing I'd recommend. Of course, the problem is identifying a sociopath when they walk in the door in the first place…
Lovely fantasy, but again, not realistic in the slightest. Again, the issue is identifying the sociopath in the first place… for that matter, how do you accurately recognise the wife-beater when they turn up in a suit and tie? The abusive parent when they walk in the door? The fact is that you can't. Obviously, should you become aware of it, it's a good idea to remove that person from your school… but you won't be able to stop them going somewhere else, for the record.
Oh, and "martial arts is like having a gun"? Ha! Not overtly…
Frankly son, you clearly don't understand how lunatic you came across (and, honestly, continue to).
Great. So what?
Okay… that's a fear you have… tell me, are you commonly associating with people who carry weapons and assault you? How much do you realistically expect to need such a specialised defensive skill? And what weapons do you think you'll need to defend against? What will be the most likely scenario? Is it an attack, or a threat? Do you understand the differences?
Then you really should have chosen better, as it implies a result, not a level of training… and a fantasy based one at that.
For one thing, no-one mentioned the term "psychopath"… they said "sociopath"… a bit different… for another, do you want a list of psychopaths (and sociopaths) who have families? Do you really think one precludes the other?
So… you want to be a "Human Killing Machine" (incidentally, that can be read two ways… a person who is a human embodiment of a killing machine, and someone who is a machine at killing humans… hmm), you want to be "known as the most lethal person on the planet"… but you would "never kill someone"???
Dude, can you see the issue here?
Lose the fantasy based rhetoric, you just look like a fool.
You're in Sydney, and you think this is all that's around you? Dude… I could point you in the direction of some arts that are far more seriously in line with what you've asked for… but frankly, you've failed completely at being even close to being suitable to be offered an introduction…
You really might want to look at your own posts, then.