Deleting K2 artifacts and uninstalling K2 for SharePoint from your environment will remove K2 artifacts from within SharePoint. You want to be sure that all SmartObjects, Views, Forms, Service Instances are completely removed from the K2 environment and that there are no orphaned artifacts. Read the Removing K2 artifacts and integration from SharePoint topic which explains the best practices when removing K2 artifacts, ensuring that all elements are removed and are no longer visible in the database, K2 Workspace, K2 Management Site and in the category tree.

If you run into any issues while removing K2 artifacts or K2 for SharePoint from your environment contact your regional support for assistance.