Eva McCulloch also known as Mirror Mistress is a former antagonist turned anti-heroine who was the main antagonist of sixth season's second half of the Flash and its seventh season's first half. She serves as the second Mirror Master (based on the Evan McCulloch version).
Why She Sucks
The main problem with her is that Eva has nothing to do with his male counterpart Evan McCulloch, the second Mirror Master, whom was not a comported CEO in the comics.
She has the personality of a sadistic, insufferable womanchild who will never grow up and learn how to work her company, correctly.
She's just filler who is the main antagonist of the second half.
She initially comes off as a very shaken but kind woman who has been trapped in isolation for six years and becomes literally evil for no reason.
She is indeed rubbish and very unlikable.
Despite being unlikable, she gets a lot of screentime.
Her childish motivations don't make any sense, since Eva has been having her mirror clone of Iris collect technology for her, including the Mirror gun, tried to go back to the real world to get revenge on his husband, Joseph Carver, for leaving her in the mirrorverse.
Despite viewers expected to "sympathize" with Eva, since she believed that a dimension existed with inverse properties, has been using her powers to exact her plan of "liberation", most likely from the Mirrorverse, she is actually a paranoid yet driven individual who believes solely in evidence and will do anything to achieve her goals.
She killed her husband and showed no remorse.
Eva is shown to be manipulative and pretentious to her own advantage; such as she lied to the public about the murder of Joseph Carver and framed Sue Dearbon for it, and also manipulate Iris by faking failure and pretending to be broken. She insufferable ruthless into getting what she wants by which she killed Joseph, proving how vengeful she can be, making her a villain sue.
She is one of the most hated Arrowverse characters.
Her dialogue "I want him to suffer" gets old quickly and will get on your last nerve.
Her "Mirror Mistress" costume doesn't look convincing and looks like a fashion designed modeler.
She tries to hide his secrets in public and gets really angry, but gets away scot-free.
Her actress, Efrat Dor does a weak portraying him.
In season seven, she wants to replace everyone in Central City with mirror duplicates so that she can "liberate" and start anew, which doesn't make any sense. Thus, making her goal too similar to Marvel's Jackal from the Spider-Man Comics (where he wants to replace humans with clones during the Maximum Clonage story arc of the Clone Saga).