From the repository you want to delete, click the Settings in the sidebar.

From the Repository details page, click Delete Repository at the bottom of the page.
Bitbucket displays the deletion dialog.
(Optional) Enter a URL in the Redirect to field.
Future users who try to access your repository are sent to this new URL.
Press Delete.

https://confluence.atlassian.com/bitbucket/delete-a-repository-221449698.html