I'd say The Boogieman from the Real Ghostbusters cartoon voiced by
Frank Welker. Or the heroine from Dark Shadows Josette played by Kathryn Leigh Scott leaping off the Widow's Hill cliff to avoid becoming a vampire. Her scream scared me to death! For some their portrayals were so real, it made me scared big time.

There's no doubt about this one. The character of Hattie Dorsett, the mother in the TV movie Sybil with Sally Field. The mother was played by Martine Bartlett, a character actor with a long career of playing small parts. I loved the movie Sybil (and the book) but hated Sybil's mother with a passion previously known only for Islanders and Flyers. To this day, I can't watch Martine Bartlett in anything else. If I see her on TV, I change the channel.

https://content.invisioncic.com/Mptv/monthly_2017_04/IMG_2173.JPG.3fd4c23ea95fb318b6d2f789b0d43e55.JPG