I figure this'll be a companion to my What creators did the most good to the X-Men thread. I'd like to know what creators you guys throught did the most harm to the X-Men franchise, and why. And I'm sure this'll get double the replies of the best creators thread.
My X-Men experience has been limited to mostly books I've found exceptional, so I honestly can't come up with bad X-creators. There are many creators who I've heard bad things about, but I've generally avoided their work.