The only way I can imagine this happening is for you to .. well ... kill a lot of people.
About the only socially accepted avenue for this would be in the military. Even if you do join the military, odds are pretty good you won't ever kill anyone. If you did end up in a role that lead to killing a lot of people, odds are it wouldn't actually make you particularly happy to have done so, unless you happen to be a sociopath.
If you are a sociopath, you might check into the Australian market for serial killers. You don't need any particular martial arts training, just access to weapons, isolated victims, and a disregard for human life.