In the vSphere client, when using the right-click actions on a powered on VM, 'Delete from Disk' and 'Remove from Inventory' actions are greyed out/unavailable.
VMware vSphere ESXi 6.x
VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x
This is an intentional guardrail intended to prevent accidental deletion of in use VMs.
'Delete from Disk' is a non-reversible action that permanently deletes all data associated with the VM and caution should be taken when performing this action.
'Remove from Inventory' doesn't delete any data but unregisters the VM from the host and removes it from vSphere inventory.
If it has been confirmed that a VM is no longer needed and is required to be deleted or unregistered it must be powered off first, following successful power off, the 'Delete from Disk' and 'Remove from Inventory' actions should be available.