The scene where Kate, after Esther gets away with suffocating Danny, walks up to a rather nonchalant Esther in the middle of a busy hospital and SMACKS HER IN THE FACE.
Really, it's Esther's CMOA, since Kate is immediately restrained by orderlies afterwards and her hysterical attack turns everyone, even her own husband, against her. Esther's pulling all the strings.
When cute little Max tackles Esther to the ground before she can manage to bash Danny's head in with a large rock, after nearly burning him with the treehouse. Then the look Max gives before Kate arrives on scene, clearly says: "Not this time!"