If you use the same negative keyword in every enabled adgroup in a campaign, you can reduce your management overhead and simplify the account maintenance by replacing all those keywords with one negative keyword at the campaign level.

You will see a dashboard warning regarding this issue if it exists:

Clicking on the alert above will open the below dialog box where you're given the option of selecting the adgroup negative keyword you want to replace with one campaign negative keyword.  Using the button shown below, Adalysis will create the new campaign negative keyword, and delete all repetitive adgroup negative keywords