i dont recall if this was in the show, but cersei also claims robert raped her many times. then cheated on her like crazy. look i am not apologizing for cersei's actions i dont think she is a "good" person in any respect for the era she lived in, but i cant say she is a true villain in the classical sense.
lol, if we're going to talk about the books...
She convinces Jaime to (attempt to) murder Bran.
She tries to have Arya's hand cut off, and later tries to convince Jaime to maim/kill her.
Littlefinger suggests that she had one of Robert's side-squeezes sold into slavery and her two bastard children killed.
Rumor is that Sir Hugh of the Vale's death at the tourney was orchestrated by Cersei.
Cersei tries to have Robert killed in the melee, and later actually has him killed while hunting.
Instead of owning up to being a twincester, she has Ned imprisoned, which results in his death - all this despite the fact that Ned was actively trying to keep them from being killed by Robert.
She has a whore beaten as leverage against Tyrion.
She tells the Iron Bank to fuck off, which results in who knows how many deaths due to the economic fallout and chaos.
She allows Qyburn to torture and experiment on people.
She thinks one of her maids is working for Margaery and has her tortured/sacrificed for Qyburn's experiments.
She tries to have Bronn murdered for naming his kid Tyrion.
She has one of the people that tried to help her with Bronn's murder tortured/sacrificed for Qyburn's experiments.
She tries to have Margaery framed for adultery and treason, instead of herself.
Villains can have motivations. She's still a villain in this story.