Report to Admin. This is one of my biggest pet peeves. We had a member, jefferies9, who created numerous (close to 100) incomplete checklists. Many just one card. All just to catalogue his personal collection of Gregg Jefferies cards. Once his mission was accomplished he never returned to the site, in two years. I was reporting him almost daily and Admin said they kept telling him to stop. But apparently never revoked his privileges. I'm sure there are probably a few uncorrected ones he's left behind.
Someday my cards may double in value and then be worth half of what I paid for them.