A member of the TRMK Staff has confirmed that Quan Chi does indeed rip his opponents leg off for his fatality. For now, you can only perform this finishing move when you are using Shinnok and Impersonating Sub-Zero. For some reason you'll perform Quan Chi's Leg Rip Fatality if you use Shinnok, Impersonate Sub-Zero, and do the fatality. It's especially cool if you perform the fatality while invisible: it would appear that the players own leg has turned against them! Try it for a laugh..