You can permanently delete any of your events if you wish.
Please keep in mind that all of the content in the event will also be deleted permanently. There is no way to undo this.
First, make sure you have a backup copy of all of your videos on that event. If you do not, download them.
Go to the event page, then click the Editor icon.
At the bottom of the menu, click Delete. A warning will prompt you to confirm that you actually want to permanently delete the event and all of your event's content.
Remember, this action cannot be undone, so be sure that you really want to delete your event.