@Leobosch Jeremiah Joseph Thank you for reaching out to us, As I understand you are trying to delete a tenant, in the process you are unable to delete due to Tenant Schema Extension App.
The Tenant Schema Extension App is added to the directory when the you enabled the Directory Extensions feature via Azure AD Connect.
Please share your details over email to 'AzCommunity@microsoft.com' with Sub - Attn: Givary
Tenant ID
Tenant name
Let me know if you have any further questions, feel free to post back.