What's one thing you're proud of accomplishing in the past year?
"Not strangling the living **** out of marketing, product management, and others who have been obviously promoted past their competencies. Why do you think I'm looking for another job?"
(Hmmm ... maybe I should be posting this anonymously.)
Translation: there can be valid reasons not to have accomplished anything in the past year. Yes, it can be a red flag, but it has to be taken in context and may not actually be a bad thing. But that's why interviewing is an artform still, and not a science. :-)