8. Debbie Jellinsky - Addams Family Values
Though Addams Family Values' villain Debbie Jellinsky (Joan Cusack) is undeniably unhinged, it's also made abundantly clear that she's a successful serial killer who murdered both her parents and two prior husbands.
And in the film's climax, Debbie has the Addams clan dead to rights, forcing them at shotgun-point to strap themselves to a series of connected electric chairs, which she will use to execute the lot of them.
But Debbie made two mistakes which ultimately caused her downfall: first and foremost, she didn't include the youngest Addams, Pubert (Kaitlyn and Kristen Hooper), in her plan, instead leaving him in his crib.
Apparently killing a baby is one step too far, but the rest of the family, including Wednesday (Christina Ricci) and Pugsley (Jimmy Workman), is totally fair game.
But Pubert ends up escaping his crib and, through an hilariously implausible set of circumstances, makes it to his family, where he re-routes the electric cables to electrocute Debbie instead, killing her.
Yet Pubert wouldn't have been a factor at all if Debbie didn't waste several minutes showing the rest of the family a slideshow of her prior "conquests," buying Pubert precious time to break free from his crib and defeat Debbie. You were so close to winning, Deb.