How can I make my carousel slider type to not have empty space in the end?

The carousel slider type's responsive behaviour is, that as you make the screen smaller, slides start to disappear. Because of this, it's common, that in the last "pane" you have empty spaces left. To avoid this there are two things you can done. The first one is to use the Single switch setting at your Carousel slider type's animation settings.
But if you don't want to change your slider's switching behaviour, then you can calculate how many slides do you need, which would always fill up all spaces. You can learn more about this calculation here. Let's says your slider shows 4 slides on desktop, and when you make your slider smaller, it can become 3 slides/pane, 2 slides/pane and lastly 1 slide/pane. Have as many slides, that if you divide them with any number they could be visible on they should have an exact number. For example 12 is the lowest common denominator of 4,3,2,1, so if you have 12 slides, that will always fill up all spaces. If the maximum number of slides, that is visible in your slider would be 5, then you would need 30 slides to always have all spaces filled up.