Any visual that allows you to have a dual axis should also let you synchronize the axis. For instance if I'm showing visits and distinct patients per month it looks really odd. The patient count is lower than the visit count but the patient count shows up higher on the chart because the axis is not synchronized. The end user has to look at the axis to left and the right in order to determine what the value is and often finds the incorrect insight.
This is a feature that Tableau has long had and Power BI should incorporate it soon!
A must have for combination charts; i.e., stacked bars on first vertical axis and line on 2nd vertical axis, etc.
I understand that this can be done by manually adjusting the Y-axis on the left and the right but that is a very static option and does not allow for the axis to grow dynamically as data is refreshed.