We’ve all been there! Double clicked between column headers to optimise the column widths only to have one column shoot out to forever and we can’t get to the end of it.
If undo (ctrl + Z) is way too far back and zooming out doesn’t help, then the simplest way to reign it in is to right-click on the column, select Column Width and set it to around 50 points.
You will then be able to manually adjust the column width to a reasonable size. Then either truncate the offending record or put Text Wrap on to prevent it from happening again.