Spartan 085

To use the Fatality moves you have to be on the very last bout of the match. So it's a winner from two out of three matches. If you win the first match and are about to win the second, the game will prompt you when you completely drain the opponents health bar. It will prompt you with, what else, "Finish Him." You have a couple seconds to hit a few buttons to perform the Fatality.

The buttons for the Fatality depend on the character you're playing with. Each are different and you need to be at a certain distance for each as well. Each character has two Fatalities to perform. All Fatalities depend on which side you're on. I won't use Left or Right in this answer because it will confuse you. Just remember, if you're to the right of you're opponent, back means you're stepping away from them and forward means you're stepping toward them.

Mortal Kombat:

Baraka: Back, Forward, Down, Forward, Square. Close Range.
Forward, Forward, Down, Down, X. Close Range.

Jax: Back, Forward, Forward, Back, Triangle. Close Range.
Forward, Forward, Back, Back, X. Close Range.

Kano: Back, Down, Back, Forward, Square. Close Range.
Down, Down, Forward, Back, Circle. One step back.

Kitana: Back, Back, Forward, Square. Sweep range.
Forward, Down, Down, Back, X. Sweep range.

Liu Kang: Forward, Back, Down, Down, X. Sweep range.
Down, Down, Forward, Down, Circle. One step back.

Raiden: Down, Forward, Down, Up, Triangle. Close Range.
Back, Forward, Forward, Down, Circle. Sweep range.

Scorpion: Down, Down, Down, Circle. Sweep range.
Forward, Forward, Back, Down, X. One step back.

Shang Tsung: Back, Down, Forward, X. Close range.
Down, Down, Forward, Triangle. Close range.

Sonya: Down, Down, Back, Forward, Square. Sweep range.
Down, Back, Forward, Forward, Circle. One step back.

Sub-Zero: Back, Back, Down, Back, Circle. Close range.
Back, Forward, Down, Forward, Triangle. Close range.

DC Universe:

Batman: Down, Back, Forward, Forward, Circle. Sweep range.
Down, Down, Down, Up, X. One step back.

Captain Marvel: Down, Forward, Back, Forward, Square. Close Range. Down, Back, Down, Forward, Triangle. One step back.

Catwoman: Down, Back, Down, Forward, Triangle. Sweep range. Forward, Back, Forward, Back, Circle. Sweep range.

Deathstroke: Forward, Forward, Down, Forward, Triangle. Close Range. Forward, Down, Back, Forward, X. Close Range.

The Flash: Back, Back, Forward, Forward, Circle. Sweep range. Down, Forward, Down, Back, Down, Forward, X. One step back.

Green Lantern: Forward, Back, Down, Back, X. Sweep range. Back, Forward, Down, Down, Circle. Sweep range.

The Joker: Forward, Back, Forward, Square. Close range. Back, Down, Back, Forward, Triangle. Close range.

Lex Luthor: Down, Forward, Down, Back, Triangle. Close range. Up, Up, Up, Square. One step back.

Superman: Down, Down, Forward, Forward, Square. Close range. Forward, Forward, Down, Back, Circle. Close range.

Wonder Woman: Up, Back, Down, Forward, Square. Sweep range. Forward, Back, Back, Forward, Circle. Sweep range.

Two unlockable characters do not have Fatalities, Shao Kahn from Mortal Kombat and Darkseid from DC Universe.