I want to remove an app that I've added completely from my Office 365 environment. I deleted the app from the sites I added it on before but it is still an option to be added to a site.
To completely remove an app, you will want to remove it from all sites that are using it first:
Then go to your SharePoint Admin page
From there, click on the SharePoint menu.
From there, click apps, manage licenses
Then manage the license for the app that you want to remove.
And remove the license
That will stop the app from appearing in your site completely.