Fatalities will have QTE (quick time event). Depending on which button you press to 'evolve' the fatality to its ultimate end. (think of Scorpion throwing his spear through someone, then you get 2 choices; 1- burn the spear to burn the enemy, or 2- pull them towards him for an uppercut to blow their heads off)
This sounded neat for all of one second until I realized it sounded awful in how absolutely f***ing basic it is. Keep that s*** to Brutalities.
It goes a lot deeper, each fatality has variations, i just gave a really short (and crappy) example. You get 2 QTE's per fatality, its basically a 'kreate a fatality' again but with a more personal take on it.
... this is a post from another forum