You can only delete issues in a repository owned by your personal account. You cannot delete issues in a repository owned by another personal account, even if you are a collaborator there.
To delete an issue in a repository owned by an organization, an organization owner must enable deleting an issue for the organization's repositories, and you must have admin or owner permissions in the repository. For more information, see "Allowing people to delete issues in your organization" and "Repository roles for an organization."
Collaborators do not receive a notification when you delete an issue. When visiting the URL of a deleted issue, collaborators will see a message stating that the issue is deleted. People with admin or owner permissions in the repository will additionally see the username of the person who deleted the issue and when it was deleted.
- Navigate to the issue you want to delete.
- On the right side bar, under "Notifications", click Delete issue.
- To confirm deletion, click Delete this issue.