As with many achievements in Oh...Sir! this is 90% luck
using combo's to get your opponents health down quickly before you get massive damage is one way, but you want to focus on not giving your opponent the option to make combo's himself. if your opponent just hit you with a "your mother" making sure he won't get the "your mother" in the second round will eliminate his change for a combo and thus eliminating his change on dealing massive damage.
Also, pick cleverly, if your oppononent can no longer complete a logical sentence, he can't score points at all, it's not always possible to take that chance away, but if you can, definitely take it.
Happy hunting, and most of all GOOD luck