EA SPORTS MMA

Easy, go to fight now and select any weightclass/arena/ and anything else you want to modify. Then on the fighter selection screen plug in a 2nd controller. Pick any 2 fighters for you and the dummy controller and begin the fight.

When the fight starts, just wait until there is 30 seconds left in the round. (Move both controllers around once in a while so the game doesn't pause on you) Then, once there is 30 secs left in the first round, get controller 1 (you) to the second controller. Wait until there is 20 seconds left and beat the shit out of the second player. You should get the TKO (or KO) and the achievement with about 10ish seconds left.

An easy way to do this with one controller is put it on EASY then take the opponent down and put them in a submission but don't finish it. Instead do just enough to hold them in the sub until there is less than 10 seconds, then finish it. It may sound difficult but on easy the computer is horrible at submissions and you should be able to control them no problem. If you want it to be even easier, fight someone with low grapple defense.