Looks like it's about 3.51 seconds. Just barely squeaks past the lucky shot KO on YouTube which looks to be something like a 3.54

So that was an initial (young Nick) comment. Now, more than a half dozen years later ME, (old Nick), can now do things like...compare framecounts of 2 videos...

So here's the breakdown:

I decided when the fight 'starts' is exactly the frame BEFORE 'UFC' appears on the bottom left of the screen. No ambiguity there, always the start frame of any fight. End of the fight? Not as easy to say.

There are a couple almost INSTANT Kos I've found on Youtube, but they also follow up on the ground, causing an extra 2-3 seconds before the fight actually gets stopped.

The one I mentioned in the initial post (EA SPORTS UFC 14 - 3 Second Fastest Knockout) is actually so close to my WR I kinda had to rethink things.

HOW CAN WE TELL WHEN THE FIGHT PORTION of THE GAME is OVER OFFICIALLY?!

The camera zooms in the frame after a KO lands and the in-game clock stops. Then the opponent falls, the player either follows up or doesn't, but depending on the KO shot the fighters fall at different speeds...

So I thought...maybe the frame before the camera zooms at the KO connection? But it turns out that the video I referenced ends up hitting their KO shot 2 frames BEFORE mine (ostensibly giving them the ......wait a sec......IGT RTA time WR...(?))...but then by the time their opponent falls and we're brought to the victory screens their run is 4 frames SLOWER than mine...

Yeah...it's pretty weird...

Time to update the rules I guess...?

And the timing rules...?

...ok then. I'm off.