To forcefully shut down a guest virtual machine (VM) using the virsh command on Linux KVM, use the following command:
virsh destroy <domain-name>
where <domain-name> is the name of the guest VM. This will send an ACPI signal to the guest OS and immediately shut down the guest machine without giving it a chance to cleanly shut down its processes.
Note: This method should only be used as a last resort, as it can result in data loss or corruption.