If you are using Proxmox Server and you want Delete the VM or Container then you need to open shell and then you need to run these commands
qm list - to list the VM
To remove or delete VM from Proxmox Server
qm destroy VMID
To lets all Containers on Proxmox Server
pct list
To delete or remove an unused container from proxmox server
pct destroy CTIC
hope it helps