Unsubscribe a Client Event 

Unsubscribing a client event is very similar to subscribing:

WDPortalEventing.unsubscribe("urn:com.sap.tc.webdynpro.test.portal",                              "TestEvent",                                wdThis.wdGetTestEventAction());

Make sure that you unsubscribe every single Web Dynpro view, as the subscription and unsubscription is valid only for the current view.