Cersei Lannister

She came to the marriage already a queen in her own estimation — beautiful, ferociously clever, and briefly, genuinely hopeful. Robert killed that hope inside a single night by murmuring Lyanna's name in the marriage bed, and whatever might have grown between them died right there. What replaced it was fifteen years of public contempt and private cruelty, given and returned in roughly equal measure.

Her revenge was total and patient: not one of the three royal children was Robert's. It is worth saying plainly that Robert was a poor husband to her long before she was a treacherous wife to him. The marriage was arranged to bind the realm's most dangerous house to the crown. It bound them, and the binding is what strangled him.