Jeff,
You need to access the item using the ArcGIS REST API. Here's a link to the Esri documentation: https://developers.arcgis.com/rest/users-groups-and-items/quick-reference.htm
You can reach the delete item endpoint using this URL pattern:
https://<Portal URL>/sharing/rest/content/users/<username>/items/<itemid>/delete
That endpoint will present you with a UI to delete the item including a checkbox for "Force deletion".
The item id can be found in the URL string within portal, or by navigating to the username REST endpoint:
https://<Portal URL>/sharing/rest/content/users/<username>/
Hope this helps,
Joseph Poncy
Geospatial Developer
Innovate! Inc.
Innovate!, Inc. is a Virginia-based 8(a), Hispanic- and woman-owned business delivering Geospatial, Information Technology, Security, Business Consulting, Project Management and Executive Coaching solutions to our government and private sector clients. Check us out at www.innovateteam.com.