Situation: Hung MMC console is unable to be closed.
Use get-process to find the MMC process:
get-process -Name mmc -IncludeUserName
Then use "kill" command with ID number to stop-process or kill it.
Handles WS(K) CPU(s) Id UserName ProcessName
------- ----- ------ -- -------- -----------
543 41508 19.66 14048 ME mmc
kill 14048