Any card that targets "last played" can target ones that have already left play, so long as they're still the last played (i.e. a good Kinsmen's could stop something like Death of Unrighteous that a normal negate or even Woes couldn't). I seem to recall that placed enhancements like KA are considered "played" both when placed and when used, so by my understanding it would be legal to negate an evil KA with a good one after it's been used.
