The fairly recent ad series of Madonna for Versace were pretty bad. I felt that she looked quite unflattering. She looked great in the series that she did before Gianni died, though. It's disapointing that in recent years, the brand appears more concerned with getting a "big name" than making attractive ads.
Most Estee Lauder ads are really bland, but I liked the ones with Liya.
One personal dislike was the Dolce & Gabbana ads a few years ago with Gisele that looked like they were bad scans with moire. I found it difficult to look at them.
And, it's not really a top-line fashion brand, but I hated those ads for Candies with that actress-slash-Playboy model Jenny McCarthy sitting on the toilet. And the ones with Alyssa Milano looking for condoms and other "naughty" themes that were more about titillation than shoes.