The actress ________ was a low key terrifying character

[DrNewGod]

Nobody with powers. No martial arts. No wielding axes, chainsaws or boiling bunnies. There were some actresses that were scary as piss without breaking a nail or doing a single overtly violent act (poison is allowed).

I'd nominate Leopoldine Konstantin from Notorious. Don't let the wiki photo fool you, her turn as Anna Sebastian was stone cold, low key botulism on two legs.

[caj]

Harriet Walter as Fannie Dashwood in 1995s Sense And Sensibility. Just cold as ice and so cruel and snobbish.

[DrNewGod]

Harriet Walter as Fannie Dashwood in 1995s Sense And Sensibility. Just cold as ice and so cruel and snobbish.

We really need a Like Button on these forums.

[caj]

We really need a Like Button on these forums.

And even though she wasn't shown, apparently her mother, Mrs. Farris, was even worse.

[James Cameron]

Patti LuPone in Beau is Afraid

[Android 17]

Linda Fiorentino as Bridget Gregory in “The Last Seduction”.

Greatest femme fatale of all time.

[Rev9]

Alice Krige in most movies

[ChrisIII]

Irma Bunt from On Her Majesty's Secret Service. Has a menacing presence over the whole film, with her strict matriarch thing mainly being an act to make sure the girls don't escape early or give full names to Bond that could be used against Blofeld's plan.

But most importantly she's the one who kills Bond's new wife Tracy(although under Blofeld's orders/driving) and we never see Bond get his revenge on her, at least on-screen.