Currently there is no way to delete any event from ACTIVEWorks Endurance organization account. However, you can deactivate an event and remove an event from the organization's Home page. Please follow below steps:  
  1. Close Registration to deactivate event
  2. Change Event Date to an Earlier Date to remove event from organization's Home page
Note: To view past events on the Home page, the Status drop down box must be set to All

User-added image

Note: To hide a deactivated event on active.com, you can unpublish it by unchecking the box next to Publish your event listing on ACTIVE.com (it may take up to 24 hours for your event to appear) mentioned in Publish Event to ACTIVE.com