I'd have to say that the saddest example was Gordon R. Dickson's novel Time Storm (1977), where after decades of novels with no (or at most a very few) female characters, he gives the protagonist a female companion and has the main villain in the first half of the book be female. It was clear that Dickson was trying to write more and better female characters. Unfortunately, all he could manage was plucky girl reporter (for the companion) and shrill bitch (for the villain). So, the absolute best he could do was cheap and offensive stereotypes. I noticed that at the time, and it definitely made me sad.