My criteria for a misbehaving author all relates back to ethics.
I have seen authors create multiple bogus accounts on sites that review books, such as Goodreads and Amazon, and rate their book 5 stars. Most times there is not an actual review attached, and if there is it happens one of two ways: a short, one-sentenced opinion in the vein that this book is awesome and go buy it!, or such an ingrained review it is definitely from a reader. It also inaccurately inflates review ratings, which also raises promotion – basically for free. To authors, this means the potential earnings just went up. This is unethical on so many levels.
In the most recent years it has come to light that a handful of authors have crossed a very distinctive line. Instead of accepting constructive criticism and less-than-perfect reviews, authors have personally berated and hated on reviewers. That’s just not cool. Yet some have gone even further as to stalk reviewers, post personal information and disparage their lifestyle. There have been a few who have outright threatened reviewers. That goes way beyond crossing all professional and ethical lines and far oversteps the author-reviewer relationship bounds. There is no need for any of that. It gets blown up all over the internet, and even other others call you out on it. You effectively dig yourself your own grave by the damage done. It costs $0.00 to be a decent person and just say, “Thanks for your review. I appreciate you taking the time to read and review my book.” It could cost you a lot of money by activating full-on stalker mode.