i agree with scorpion569

MK1: Raidens head pop
MK2: Kung lao slice
MK3: Sektor Sqiush
MK4: Fujins tornado n cross bow
MKDA: Quan chis neck stretcher LOL, nah just kiddin, Cyraxs claw grab
MKD: A draw between scopions leg spear thing and barakas blade rage

thats it for me

MK: Rayden - Head Shock
MK2: Scorpion -Throat Slice
MK3: Sheeva - Skin Rip
MK4: Quanchi - Leg Beat
MKDA: Sub Zero - Skeleton Rip
MKD: Mileena - Nibbler, Sub Zero - "Going so Soon?", Baraka - Torso Tear
MKSM: Fatality done on Reptile

Or the the Bunny beatdown he does in MKSM. I swear that rabbit mustve been filled with a anvil or something to do that damage to someone.

but seriously if i had to pick the goriest fatalities, the the top five in mind are:

Raidens Head Pop -Mk1
mileena Multi-stab - MK2
Kung Lao Hat slice MK2
Subzero skeleton pull -MKDA
Jades Stick Shake-UMK3

Mileena's head bite in MKD.

The Fatality that I really liked and I thought it was sick was Hotaru's neck break.
It makes me cringe up.
He kicks your legs out from under you where you are on your knees then he gets behind you and turns your entire head around three times.
Then you finally fall over with the neck just dangling there.
Awesome fataltily, not bloody, but it looked realistic.