Cassidy Freeman stars as Tess Mercer on Smallville.  While Lex Luthor is away, Tess is in control of his company and runs it aggressively.  We think Lois Lane put it best when she said, "Tess Mercer is a pit bull in Prada."

Tess Mercer Quotes

Tess: Fix the situation, Stuart. Or I'll have you terminated.
Stuart: Okay, By terminated, though, you mean fired, right? Right?

Lois: I just came to tell you that I'm not leaving the Daily Planet.
Tess: You were never leaving, Lois. I fired you.
Lois: Well, I'm not going to get into the whole "she said, she said" thing with you.

Smallville Quotes

But if you look at history the great men and women of the world have always been defined by their enemies.

Lex

Everything okay, Smallville?

Lois