There are a couple of verbs — both of them used at times for dialogue attribution — which might as well be specialists in character assassination.
One (and I have Teresa Nielsen Hayden to thank for the tip) is “whined.” As soon as a character whines something, he or she loses the respect of the reader. Heroes don’t whine. Strong villains don’t whine, either. If you want your readers to dislike some character, all you need to do is hint that the person might have whined at some point.
The other verb is “to smirk.” Only smug, self-satisfied characters smirk. Likeable characters don’t. A smirk is not a smile; nor is it a grimace; and it doesn’t substitute for either one of them.
(I’ve been fighting that fight for going on four decades now. I’m nothing if not persevering about these things.)