Hi Ben, welcome to Absolute Playstation. Here is the information you need:

Mortal Kombat: Armageddon features a Kreate a Fatality gameplay
mechanic. This innovative feature is brand-new to the Mortal Kombat
universe and adds a very unpredictable nature to the end of each and
every match; hypothetically, each Fatality could be different (i.e.
stringing together different chain animation moves to create different
Fatality outcomes). Once an opponent has been beaten two out of three
times, they become dizzy. It is now time to input the Fatality button
combinations. Once the buttons have been successfully inputted, a
meter will appear. Once this meter depletes completely, the Fatality
sequence ends. So as long as you are fast enough to continue entering
button combinations, the longer the Fatality sequence; you can string
up to 9 chains and end your sequence with a Finisher for 10 possible
actions. Note that some of this information (button combinations and
names) has been borrowed from Prima Games’ Official Game Guide to
Mortal Kombat: Armageddon.

Mortal Kombat Armageddon Chains:

The different animations are divided into categories. For
example, chains are the actual attack animations (kneeing your opponent
to the head, slapping their face, ripping out a rib ect.). These
precede the ending to the sequence or Finisher. Each time you input a
chain combination, your meter refills but begins to deplete faster than
the last one. Remember that you cannot enter the command of a new
chain until the previous animations has been completed. All in all,
you can string together 9 chains (some chains can even be repeated
throughout the string). Chains usually end with a Finisher, which is
detailed below.

Mortal Kombat Armageddon Transitions:

The purpose of transitions is to maneuver your opponent into a
specific position to inflict more damage upon him/her; they do not
cause any damage to your opponent, nor do they count as one of your 9
possible chain animations. Different chains become available to use
depending on your opponent’s position. After using a transition, the
Fatality timer resets to the exact amount of time you had before you
used the transition. Transitions are merely used to set up your
opponent in a position for further punishment. Transitions can also
consist of pulling out a sword that only a handful of characters can
do. These characters are: Scorpion, Sub-Zero, Sareena, Li Mei, Ashrah,
Dairou, Kenshi and Shang Tsung.

Mortal Kombat Armageddon Finishers:

Finishers represent the ending to a sequence of chains. They are
usually the most brutal and consist of decisively killing your opponent
in a variety of ways. It is also possible to start a Fatality sequence
with a Finisher and end it with a Finisher giving this Kreate a
Fatality feature a little more depth.

Mortal Kombat Armageddon Fatality Rating:

After you perform a Fatality sequence, you are rated depending on
how many chains you strung together end with a Finisher. Note that if
you don’t end your chains/transitions with a Finisher, you will not be
rated. Below is a list off the different ratings and how many chains
need to be achieved in order to obtain that rating.

Mortal Kombat Armageddon Fatality – 0 chains
Mortal Kombat Armageddon Deadly Fatality – 1 chain
Mortal Kombat Armageddon Killer Fatality – 2 chains
Mortal Kombat Armageddon Bloody Fatality – 3 chains
Mortal Kombat Armageddon Mortal Fatality – 4 chains
Mortal Kombat Armageddon Brutal Fatality – 5 chains
Mortal Kombat Armageddon Evil Fatality – 6 chains
Mortal Kombat Armageddon Vicious Fatality – 7 chains
Mortal Kombat Armageddon Savage Fatality – 8 chains
Mortal Kombat Armageddon Extreme Fatality – 9 chains

Every character has “access” to basically the same animations, but
the way you string them together is entirely up to you. Please note
however that only certain bosses (Blaze, Onaga, Goro, Kintaro and
Moloch) can perform Fatalities; Shao Kahn cannot. Also of note,
Fatalities cannot be performed on Blaze. These boss characters have
their own respective chains and Finishers listed below. The lists
below contain all the different chains, transitions and Finishers with
their respective button combinations.

Mortal Kombat Armageddon Controls:

Walk Forward - Directional Button Right
Walk Backward - Directional Button Left
Walk Out -Directional Button Up
Walk In - Directional Button Down
Jump Forward - Directional Buttons Up and Right
Jump Backward - Directional Buttons Up and Left

Attack 1 - Square
Attack 2 - Triangle
Attack 3 - X
Attack 4 – Circle
Block – R1
Change Fighting Style - L1
Throw – R1
Pause – Start