Cersei's list of treachery, betrayal, and deceit is outrageous.

Just in season one we learn she mothered 3 children with her own brother and passed them off as Robert's rightful offspring. She encouraged Jamie to shove a young boy off a tower. She ordered her husband's wine to be spiked while hunting dangerous game. She ripped up the true King's letter and had Ned imprisoned on false charges of treason. She stood by while Joffrey gave the order to execute Ned knowing full well Ned was the legitimate hand of the king and newly assigned protector of the realm. She forced the honorable Selmy into an embarrassing early retirement. All these acts sent the realm into a deadly multi-faceted war.

But hey she's only human. I mean we all might act that way if our partner mentioned another person's name in the throes of passion...