Anyone else  having a problem getting this one?? over 100 fights and i have had no luck

... It's just luck really. I knocked out Machida with a left hook that probably shouldnt of knocked him out. But I'll take it.... Keep trying

still going :P  knocking out other achievements and almost finished with a Lightweight career  but no KTFO achievement

Got it on my 4th career fight lmao

They had a similar achievement in 2009.  It wasn't that tough for me on that game.  I have little to no intention of playing this one, though...sadly. 
 
However, I think the name of the achievement is hilarious, and I can't help but think of Friday right now.

Meh this one is really bugging me. I've been trying for it throughout my career but now I'm taking mostly everyone to the ground. Sick of trying for this. I have done exhibition and had some quick KO's without rocking my opponent first but to no avail. That, I believe, is a flash KO. Correct me if I'm wrong?