You can use dual axis.
Unfortunately, that's NOT a "stacked bar". See that the Budget values go up it steps (each division) and then the Actuals values gently increment.
If this was a stacked bar the pattern would be less obvious. This is simply a dual axis with but measures starting at 0.
I understand your initial idea is to stack the two bars so you can show if the actual has already met or not the budget.
My suggestion is, instead, use a reference line for the budget so you will have the bars only representing the actuals measure. It will give your audience a cleaner view and the rapid insight you want to provide.
1- Move your SUM(Budget) green pill from the rows shelf to under the Sum(Actual) marks card on the left. This will remove the bottom chart from the screen
2- Go to the Analytics pane and drag a Reference Line over the chart. Drag it over the Cell square that shows up
3- On the Edit Reference Line, Band or Box, select the Value to be your Budget. You can also add the Label to be the Value.
4- Edit the Reference line color to be a darker gray or red and it should be done.
Note: I would also suggest flipping the viz. You should get something like this at the end.
Definitely If you're trying to compare Actuals to Budget then a bullet graph is the way to go and not a stacked bar at all.