i don't get it why most people would immediately jump into a conclusion that MMA or those that we see on TV are the most deadly arts and techniques. first of all, what we see on TV are sports and those are bound by rules hence those techniques applied are backed up with safety, unlike in a real fighting scenario where the match would end if either one is badly injured or worse, dead. and second, most of those techniques aren't tested and proven in a real street, no holds barred fight and in fights dealing with multiple attackers.
if ever there's this most dangerous martial art or technique, i'm pretty sure that it is very well kept by grandmasters and experts that even champions and hard core enthusiasts don't know.