Before you read this solution, be warned that great reaction time, analog stick placement, and patience are the way to getting this achievement...i used Juergen to get this because of his great side to side movement and his spin. you can easilly use the "Ace the Serve" method mentioned in the other guide in order to get all the way into the final tournament and then this is where the serve becomes almost useless.
When i used Juergen against Jun Soo and Mark, about 10 tries into getting owned by Jung Soo, I found that hitting across the table close corner shots with "focus" being used will either make the cpu do a bad shot or put the ball into position for an easy shot to the other corner for a point.
So another way to say this is that if you were on the left corner of your side of the table and you wanted to hit it into the right side of the opponents side of the table, then you would click A and B (hold if you have time to charge the shot) and then aim your left analog stick down and to the right so that the shot is aimed close to the net and at the corner. With Juergen's great spin it made the cpu get into a bad position for him to hit the next shot... and then if you wanted to hit it left, press A and X (possibly charge it) and aim the left analog stick down and to the left.
The part that helps to get the cpu into a bad position is any focus shots you can use by holding RB and then doing which ever shot you were planning on hitting... this is best saved for when you feel that the cpu can be put out of position or if it can help bury a ball in the opposite direction of the cpu's location.
Just try to hit the ball to the opposite corner every time or else the power of both Jung Soo and Mark can kill you when you hit a same side shot. Using this method on both jung Soo and Mark I was able to beat Jung Soo 11-7 11-5 and then Mark 11-7 11-4.
Hope this can help you.. any questons or side notes that can help in this solution should be put into the comments.