Like others on this list, Scorpion could, of course, be beaten. That doesn't mean he isn't acknowledged as one of the bloodiest, most badass characters in video game history.
Anyone who ever played Sega's initial Mortal Kombat game knows that Scorpion was the least desired character to play against, as his shout "Get over here!" was often followed by a go-to finishing move that dragged his opponent across the ground before finishing him.
Point bank: Scorpion is one of the most cold-blooded killers ever.