The most simple way i found to do it was use a second controller. Stay as the same fighter on controller 1 and change each fighter on controller 2. As soon as the round starts it will take 6 or 7 hooks to down controller 2 then a last to finish him. Obviously let the 10 count go through.
It took me about 1 1/2 hours to get through all the fighters. Remember to fight 'yourself' as well. I started at heavyweight through to bantamweight. The acheivement popped when i had reached the count of 10 on the bantamweight fighter. As mentioned before this acheivement dosent require you to beat the locked (Dr pepper promotions). It does require you to beat the games fictitious players as well as real world fighters. Im not sure if these are locked if you havent completed the champion mode as i had completed the story before attemping this.