Here are the worst and evilest Loud House characters:
Doug and Michelle: Luna Loud's enemies
Dr. Linnaeus: Lisa Loud's enemy and evil scientist
The Two Ace Savvy Movie Judges: Lincoln Loud and Clyde McBride's enemies and Bill Buck's evil judges/staff
The Miller Family: Lincoln Loud and Clyde McBride's new enemies
Mr. Bolhofner: Lincoln Loud's evil math teacher (since Mr. Blunt is Milo Murphy's future enemy)
Aunt Ruth: Wasn't evil, but the worst family member of the Loud Family