Spoilers for 4x03. Just thought I'd add in a scene to a terrible episode to make it - well, not as terrible.
As Arthur turns to leave, Gwen looks back on the dying King. Vaguely, behind her back, she hears the door shut.
"You murdered my father." She says, calmly. There is no laced hatred, just a simple fact.
Guinevere continues on.
"You slaughtered a blacksmith based on a false accusation. You killed a man trying to provide for his family. You took the life of someone who served you until his dying day."
Her voice is shaking now, but Gwen does not cry. "I should hate you. You threw me in the cells for committing absolutely nothing time and time again, you condemned me to die more times than I should ever have been accused. I should hate you with every fiber of my being."
And then she lets out a breath. A huge sigh, as if trying to force everything out of her chest. She stares straight onto Uther Pendragon's face.
"But I don't. I never have. Five years and I have never looked upon you with hatred, And – " Gwen tries to control herself, because now she can feel the tears forming. "And if you have an ounce of mercy left in your body, you will live. You will live for your son who has defied you more times than either of us can count, yet he is the one who loves you the most. You will live for Arthur."
And with her last words spoken, Guinevere turns to follow the path out the door. She leaves the mighty King, pale and barely giving a breath, to sleep.