Hi @mevo ,
Use the below action and sort it by File size in the advanced section

This action provides an output variable called %Files%
If you sort it in Descending order as shown above you will have the largest file at the top of the %Files%.
Then in the Delete action use %Files[1:]%
The syntax is %Files[StartIndex:StopIndex]%
But if you start from 1 and don't give the StopIndex as %Files[1:]%, this tells the Delete Files to skip the 0th element (which is your largest file), and take the rest till the end of the list

I recommend you to do the Delete action at first on some sample files to avoid any accidental deletion.