Had Machiavelli written a book on insults, this is the book he would have written. He would have suggested calmly wounding your enemy with a tailor made barb without coming across as if you've been wounded yourself. Often the best putdown is a comment which seems on the surface to be well intentioned. And ham-handed attempts to relate or sympathize can be the most effective ways of underlining your opponent's weaknesses. These are far more humiliating than any angry outburst could ever be. Learn how to eviscerate the proud homeowner, the would-be tough guy, the bully, the boastful parent, the second guesser, and many others.
Machiavelli would also have suggested having these insults ready beforehand, since, despite the old clich, revenge tastes best when it is a dish served piping hot.