From the section 'Using the ESXi 5.0 esxcli command to power off a virtual machine' in KB1014165 at the VMWare Knowledge base:
The esxcli command can be used locally or remotely to power off a virtual machine running on ESXi 5.0. For more information, see the esxcli vm Commands section of the vSphere Command-Line Interface Reference.
Open a console session where the esxcli tool is available, either in the ESXi Shell, the vSphere Management Assistant (vMA), or the location where the vSphere Command-Line Interface (vCLI) is installed.
Get a list of running virtual machines, identified by World ID, UUID, Display Name and path to the .vmx configuration file, using the command:
esxcli vm process list
Power off one of the virtual machines from the list using the command:
esxcli vm process kill --type=[soft,hard,force] --world-id=WorldNumber
Note: Three power-off methods are available. Soft is the most graceful, hard performs an immediate shutdown, and force should be used as a last resort.
Repeat step 2 and validate that the virtual machine is no longer running.
I hope this helps :)