Directory /proc/vz not found, assuming non-OpenVZ kernel
Container init failed: Cgroup is not mounted
TASK ERROR: command 'vzctl destroy 100' failed: exit code 5
TO delete just navigate to /etc/pve/nodes/xxxx/openvz/ and delete the file which has the vm number. Mine was 100.conf
$ rm 100.conf
This will completely delete the node.