MK Ninjas... I mean all you really need is Noob Saibot and Ermac and you call it a day.
But I would watch the Mishima clan closely... mainly Heihachi. Call him old (or young now as of TTT2), but he has survived every attempt on his life thus far.
-thrown off a cliff by Kazuya, survived without having to sell his soul to the Devil.
-punched through a wall by Devil Jin and fell to the ground, survived.
-Took a full force explosion by an ambush of JACKs, flew 28 miles and survived.
-caught a fukkin bullet with his teeth
whereas, Jin was born with the Devil gene, and Kazuya and Jinpachi both sold their souls to the Devil.