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Krav Maga is deadly as Midwest 2 said. The purpose is to teach you how to take on multiple attackers at once and either maim them seriously or kill them. It is taught to Israeli Special Forces and is extremely deadly. If someone knows Krav Maga well they can take on 3-4 or more people and kill them in a matter of 10 or so seconds or hurt them badly.
Systema is very similar and is also quite deadly and meant to take on multiple assailants.