Go to a chess match. Once there and fighting, kill the opponent's leader with whoever you want to do the fatality with. If you defeat him pr her, a fatality will automatically happen.

Go to practice or arcade mode and pick Shujinko. Then, go to the Slaughter House level. When the match starts, knock your opponent down into the basement of the Slaughter House. Next, get on your opponent's side so that you are moving them back toward the death trap. Make sure not to push them all the way back. Next, pop them up into the air with Away, Y(2). Then, while in the air, do Liu Kang's Bicycle Kick. The last kick should send your opponent flying through the air and into the death trap. Once your opponent has been diced up into little pieces of flesh, it should say under your name. 13 Hits, 127% damage. You should have two hits from the pop-ups and ten from the bicycle kick making that 27% damage, and one from the death trap, which automatically kills your opponent and gives you 100% damage. Note: You must have Liu Kang's Bicycle Kick from Konquest mode.