User blog comment:NightmaresRevenge/Calling for help on the Amazing World Of Gumball wiki/@comment-29191679-20190720002152

If you need to delete a page but can't do it yourself, you can ask a staff member to do it. You can also add the template to that page to mark it as a candidate for deletion.

Now, that person probably vandalized some existing pages as well. You can revert such changes on any page by looking up that page's history, finding the latest version that hasn't been vandalized, and restoring it (by clicking Edit, then saving the page without making any changes).