Say that you are observing someone in a position of power. You have good reason to believe that this person is falling prey to a known cognitive bias, and that this will tend to affect you negatively. You also can tell that the person is more than intelligent enough to understand their mistake, if they were motivated to do so. You have an opportunity to say one thing to the person - around 500 words of argument. They will initially perceive you as a low-status member of their own tribe. The power differential is extreme enough that, after they have attended this one thing, they will never pay any attention to you again. What can you do to best disrupt their bias?
This is clearly a setup where the odds are against you. Still, what kind of strategies would give you the best odds? I've deliberately made the situation vague, so as to emphasize abstract strategies. If certain strategies would work best against certain biases or personality types, feel free to state it in your answer.
I'm making this a post of its own because I find here much more discussion of how to overcome or subvert your own biases, somewhat less of how to recruit rationalists, and almost none of how to try to overcome a specific bias in another person without necessarily converting them into a committed rationalist overall.