Hello there,
Technically you could as Sharepoint Online (SPO) admin delete the site so no user can access the content using PowerShell: https://learn.microsoft.com/en-us/powershell/module/sharepoint-online/remove-sposite?view=sharepoint-ps
However, you can also Remove Users Profile from the OneDrive site manually or using PowerShell by following the steps described in the section https://learn.microsoft.com/en-us/sharepoint/remove-users#site-by-site-in-sharepoint
- You'll need to be site owner to do that and that is possible to make your admin account owner of the site and that is possible to do on https://admin.microsoft.com/ > Active user List >Select User > OneDrive tab > Create LInk option. In the case the account itself is deleted you can use the following PowerShell cmlet: Set-SPOUser -Site <URL> -LoginName <UPNofDesiredAdmin> -IsSiteCollectionAdmin $True (Reference https://learn.microsoft.com/en-us/sharepoint/restore-deleted-onedrive ; this article is somehow unrelated but has the cmlet in any case).
I hope this helps!
-DF