I'm gonna be in the minority here, and say that IMO, DS9 did more damage to the Ferengi race tha any bad episode of TNG could ever have.
TNG gave us the Ferengi, and at first, yes, they were awkward, comedic, and not taken seriously. However, when season 3 of TNG came around, thank god that began to change... the Ferengi finally felt right... the episode with the Barzan Wormhole gave us duplicitous Ferengi that were much more serious and believable. THAT was how the Ferengi should have remained.
But DS9 totally killed any semblance of integrity to the Ferengi. The Nagus was a joke, Moogie was a joke, and they took the Ferengi need for profit to ludicrously silly levels... the "Divine Treasury"? C'mon...
The writers of DS9 had one thing in mind only... to use the Ferengi to make us laugh. Not only did it fail... it grew horribly tired and old.
There WERE a few good war episodes with Nog, this is true... and I DO give them kudos for at least trying to handle Nog in a decent manner... but Rom, Quark, and Brunt always seemed like the typical funny alien material, and I hated it.