Near the bottom of each divider between columns in Finder there are two little horizontal bars that when clicked and dragged resizes the column to the left. This is great, but since the last column doesn't have a divider to the right of it, how can it be resized?
The last column isn't actually a column, strictly speaking, it's a preview.
The only way to resize it is to enlarge the overall window, which can be a bit irritating if you are a lot of levels deep…
You can try Alt/dragging one of the columns smaller, which will change all of them. Then, allowing for a bit of a screen bug which means you need to change the window size slightly, you can gain as much room as possible for the final column/preview
Graphics glitch/screen bug …
Make the Finder window larger than the sum of the column width, and you will get a bar you can drag to resize.
Using the example image below, this was achieved by grabbing the resize bar between "Size" and "Kind" and shrinking the Size column just a tad. This allows you to expand the "Kind" column.