The Serpent's Fangs (Aemond x oc)

Ever since she had taken his eye, Aemond has always seen Visenya as she is. The eldest bastard of the heir was no dragon. She was a snake slowly slithering around the Red Keep's edge, waiting for the chance to deliver the finishing blow.

And Aemond was the only one who knew of the threat she proposes.

Or : read about two sociopathic lunatics that drove the realm to war only to kiss afterwards.