She may not have occult knowledge or magical endowments but there is no argument against Lady Tremaine being one of the wickedest Disney villains ever. Her lack of those is more than counterbalanced by her malicious unkindness. 

At the receiving end of such negative vibes is her stepdaughter Cinderella, hero of the eponymous 1950 Walt Disney film.  

Cruel and scheming, Lady Tremaine could put to shame anyone dreamed up to the same effect by Edith Wharton. Tremaine basically does not allow anyone else to be happy in Cinderella's own house other than herself, her daughters Drizella and Anastasia, and her diabolic cat Lucifer.

Her machinations emanate from her desire to secure wealthy sons-in-law and thereby improve her lot in society. Badly enough, she is always one step ahead of everyone in the film. When she isn't, she trips them in more ways than one. 

Lady Tremaine has the most recognizable actor in Eleanor Audley, who voiced another spectacularly cruel Disney woman: the fire-breathing, ice-talking Maleficent.

Lady Tremaine and her voice talent Eleanor Audley

Unlike that villain however, Lady Tremaine is the kind to inflict psychological more than physical cruelty. Her power lies in her words, not an enchanted staff. People, in fact, call her the Wicked Stepmother more often than Lady Tremaine.

Picture the dire consequences then if Lady Tremaine gets hold of a magic wand. Disney explored this what-if at length in the direct-to-DVD sequel Cinderella III: A Twist in Time.

Susanne Blakeslee takes over the duties of the dearly departed Audley in this film. Blakeslee also voices Maleficent in the Kingdom Hearts series.