Ok while its really cool to see the finishers movesets being listed, it never quite tells us what to expect to see. Seeing Kitana and Sonyas 2nd finishers being listed as 'Kiss of death' doesnt really tell us much of whats going on during the actual finisher so I've opted to collect up all the fatality information and provide a moderatelly detailed description, being that I've been a rabid MK fance since the very first game way back when in the arcades I feel its important to know what fatalities do what as oppossed to just how to perform them.

So here is all the fatalities and heroic brutalities with descriptions that are known. I'll do my best to update this as the days pass.

I've also listed the finishing moves motions, I think this is from the x-box version I got the info from here.

http://www.fdmk.net/?mode=mkvsdc§ion=kombatants

(Dont mean to advertise though, I want to give this guy credit for providing the info is all) (UPDATED 11/15)
SONYA #1
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Fatality #1: D,B,F,F 4
Neck breaker. Performs her MK4 'throw' which involves doing a headstand on the kombatants shoulders and snapping their neck.

fatality#2: D,D,L,R 1
(unseen)
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CAPTAIN MARVEL #2
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Heroic Brutality #1:D,B,D,F 2
An uppercut followed by lighting strike which knows kombabt into the ground, finnal he shoots into the air and flies feet first into the kombatant embedding them deep into the pavement, you see their hands and legs twitching from this blow.

Heroic Brutality #2: D,F,B,F 1
lifts th ekombatant over his head and slams them headfirst into the ground, they kombatant is stuck headfirst int he hard floor their legs poking otu and slightly twitching, pretty cool and funny if you ask me.
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SCORPION #3
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Fatality #1: D,D,D 4

Toasty! His classic toasty is back after dissapearing for 3 games. You know the drill, removes mask, roasts opponent and their charred corpses drops to the floor smoldering.

Fatality#2: R,R,L,D 3

Descends into a Lava pit below which dissapears, then appears under the opponents feet and they sink into the lava pit screaming. A charred Skeleton is spat out of the pit followed by Scorpion teleporting back into frame.
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KITANA #4
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Fatality # 1: F,D,D,B 3
Kiss of death, they swell up really huge...and burst into bluish smoke and light, their full skeleton drops from the sky after the cloud dissipates.

Fatality # 2: B,B,F 1
Fan Impalement: Throws one fan then the other into the opponents chest, dropping them.
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SUPERMAN #5
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Heroic Brutality #1: D,D, F,F 1
Over head smashes, Devilvers several hard hits to the Kombatants head driving them deeper into the ground until they're up to their arm pits adn dazed.

Heroic Brutality #2: F,F,D,B 4
(Unseen)
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THE JOKER #6
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Fatality #1: B,D,B,F,2
Head shot, we've all seen it in its glory at least. Pulls out a gun, pulls the trigger and a 'BANG' sign apepars confusing the kombatant while the Joker laughs, followed quickly by him drawing arela pistil and firing a single shot into the head...which now appears off screen as per the ESRB's request(groan).

Fatality #2: F,B,B 1
Straight flush: He presents soem cards then begins throwing them into the kombatantchest, hips, and finally forehead killing them. This is a cariation of Reikos MK4, and SMokes MK:Deception shuriken fatality.
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SUB ZERO #7
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Fatality#1: Grabs the kombatant and raises them above him, and then feezes them and finally slams their frozen carcas onto the floor shattering them all over. variation of his MK3 lift and freeze fatality.

Fatality #2:(Unseen)
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THE FLASH #8
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heroic Brutality #1: D,F,D,B,D,F 3
Runs in circles around the kombatant creating a whirlwind rraising them into the air, followed by him jumping above them and delivering a feirce hit slamming them into the ground.

Heroic Brutality #2:B,B,F,F 4
Basically he beats the crap out of them from a few different angles, has to be seen to be enjoyed :P
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JAX #9
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Fatality #1: B,F,F,B 2
Grabs kombatant and throws them in the air, as they fall he draws his machine gun and fills them with lead.

Fatality #2: F,F,B,B 3
Draws his hands back adn delivers a head clap. Variant of his MK2, MK4 head splatter fatality..only here it doesnt decapitate the opponent, looks like its just a head crush with no gore or blood.
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WONDER WOMAN #10
__

Heroic brutality#1: F,B,B,F 4
Whips her golden Lasso around the kombatant, jumps high into the air spinnin gthe kombatant around clockwise before slamming them into the pavement below.

Heroic brutality#2:U,B,D,F, 1
Whips her lasso around their chest and pulls it back spinning them, they eventually spin arm deep into the floor dazed.
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CATWOMAN #11
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Fatality #1:F,B,F,B 4
Lashes the kombatant with her whip and yanks them towards her, they ar epulled skidding on the ground chocking as she does this before place afoot behinf their neck and snapping their neck with a good hard pull on her whip.

Fatality #2:D,B,D,F 2
places her claws on the kombatants face and slashes downward, the jams one clawed hand into their gut and flips them over and slams them to the floor.
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SHANG TSUNG
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Fatality # 1:B,D,F, 3
Grabs kombatant by throat and steals some of their soul, releases them and they drop to the floor, he then slams his foot into their back breaking it and consumes what remains of their soul.

Fatality#2: D,D, F,F 2
In apuff of smoke turns into the kombatant, grabs them by the throat and steals their soul, hey collapse to the group kind of whitish and he returns to his normal self.
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BATMAN #13
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Heroic brutality #1: D,D,D,U 3
Throws a Batarang with sonar and the kombatants are engulfed by bats and collapse and freak out, still being engulfed by bats.

Heroic brutality #2:D,B,F,F 4
Punches kombatant spinning them so they face away from him, he then grabs them around the throat with one arm and fires his grappling hook into the air and the two of them fly off screen, a few seconds later the kombaant hits the floor with Batman standing on their chest.
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LIU KANG #14
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Fatality #1: F,B,D,D 3
places his hands together which are now covered in flame and...and MK1 machine drops onto the kombatant and they get squished. Much better version than the MK3 one, but still, meh

Fatality #2: D,D,F,D 4
Hard to describe as the video quality wasnt very good, He uppercuts the kombatant, delivers a bike kick to their head and then blasts them with a fireball.
------------------------------------

GREEN LANTERN #15
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Heroic brutality #1: B,F,D,D 4
Captures kombatant in a green sphere, and then abrupty compresses it breaking the kombatants back. The then releases the kombatant and they drop to the floor like a rag doll.

Heroic Brutality #2:F,B,D,B 4
(unseen)
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RAIDEN #16
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Fatality#1: D,F,D,U 2
Grabs the kombatant by the throat and fills them with lighting, they get the shock treatment for a few seconds before a bolt of lighting strikes them from above, burning off all the meat leaving a charred skeleton which collapses to the floor.

Fatality #2: B,F,F,D 4
(unseen)
---------------------------------

DEATHSTROKE #17
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Fatality #1: F,D,B,F 2
slashes kombatant accross the chest, dropping them to their knees, and then snaps their neck to finish them off.

Fatality#2: F,F,D,F 2
Thrusts his sword into the kombatants gut and takes a step back, draws a pistol an dfires a single head shot(camera backs away the same as the Joker's fatality)
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KANO #18
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Fatality #1: B,D,B,F, 1
Draws one knife from one boot and throws it into the kombatants chest, followed by the second knife in the other boot.

Fatality#2:D,D,F,B 4
(unseen)
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LEX LUTHOR #19
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Fatality#1:D,F,D,B 2
(unseen)

Fatality#2:U,U,U 1
Presses some buttons on his arm pad and lock on symbols appear on the kombatant, dozens and dozens of missles strike them leaving a charred corpse(sadly no chunks or bits)
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BARAKA #20
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Fatality#1: B,F,D,F 1
Slashes kombatant accross the chest, then the stomache, the skewers them in the chest with both blades and lifts them in the air, followed by a suplex which slams their body to the floor. The suplex is a variation of his old MK2 throw animation.

Fatality#2:F,F,D,D 3
Kicks opponent to the head knocking them to the ground on their back. he then jumps on them and plants his fists in their chest and the nshoots out his blades.
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Thats all the fatalities tha I've seen thus far. This description is here for all of us who are curious as to what all the finishers in the game look like, since there werent too many accurate descriptions of them all here is a compliation for your considaration.

If I make any errors or mistake feel free to inform me and I'll make the adjustments.

Hope this satisfies your curiosity.