1. This is a request to remove the user permissions across the whole Site collection.

  2. It will be time consuming to check the permissions for every list/library/sub-site that has unique permissions and remove the user from it.

  3. Hence, there is a workaround for this, where removing the user will remove the user permissions from the entire site collection. _catalogs/users/simple.aspx displays all the users, across the Site collection.

  4. Navigate to _layouts/15/people.aspx?MembershipGroupId=0

  5. Select any group/user, that needs to be removed.

    user

  6. Click Actions and select Delete Users from the Site collection.

    Actions

  7. User Permissions will be removed across the whole Site collection.