How to get two columns in legend

Hi JohnnyFonseca 
Your chart has a category and a subcategory.
(You didn't attach an example dataset, so I'll use one of my files to explain everything)

Drilling down will show the full Legend of all hierarchy levels.

There are no generic settings that allow you to do otherwise and show full levels at legend from high level.
You can work around this by importing images
Here's how it works:
1. Snip your legend as shown on the subcategory and save it as a picture.
2. Import to your report:

3. Add to your snipped image background in the same color as your graph

4. Put it on the legend place and group it with the object:

The result after drilling up :

If you want to improve the design of the legend you also can create it on power point and import .

Regarding data visualization, it's important to note that
The comparison you want to make based on the data isn't possible with pie.
It's because there's no part of the whole when there are multiple parts.

. Instead, you compare their dominance percentages (parts)

My recommendation is to use matrix and conditional bar formatting to create a table graph.
Here's an example:

Link to a sample file with both examples  

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