How can I kill an instance of akonadi from a session other than the one that started it?

Scenario: I'm logged in at the console and have akonadi/kmail running. I go away and log in remotely (via nx) and would like to be using kmail from that session. I've learned from painful experience that having akonadi running twice is disaster (I lose email, and not just the new stuff that comes in). So...I'd like to kill off the one running in the console, but "akonadictl stop" only affects an instance in my current session.