You have to hold Low Punch at the beginning of the winning round (whether it's two or three). After "Finish Him/Her" appears, get close to your opponent. Take one step back, then a split second later release Low Punch. It should work because I have done it on MAME.

It doesn't matter how long you hold it for as long as you start holding LP before the round, say, when Shao Kahn says "Round 2, Fight!" Start holding it it right as he says 2, then beat the CPU or a dummy character without even caring about how much time has gone by, by holding it before the round starts, it counts as holding it for an unmeasurable amount of time, so you could kill them in 10 seconds and still do the fatality. Also, just beat them with a standing HP, as even the max distance is close enough for the Kintaro Fatality, and as long as you don't move, you should be fine, don't release until Finish Him/Her disappears to ensure it. This a very convoluted method, but it will work. It's probably one of my all time favorite Fatalities, and I don't even care about Fatalities!

Matt