So what does Bad Daenerys suggest about power?
I.
We'd do well to be as critical and wary of powerful figures we're predisposed to love as we are of those we dislike...if not even more so.
"Love is the death of duty," Jon muses to himself during a turning point in the final episode. Our love and our esteem for a charismatic leader can lead us to rationalize questionable stances and choices that we wouldn't be so quick to excuse if they'd been made by someone else. Unconditional, unexamined love of a leader is how we first lose our capacity for critical thinking, then forget our principles, and finally erode our safety and freedom as we show a wayward leader that accountability means nothing to us, and that they can do anything they want.
II.
A good, responsible history or meteoric rise is not a guarantee of the future.
Just because a leader has generated good works in the past, or because we have loved them in the past, doesn't mean they are granted a free pass for poor choices in the present and future. People change, and circumstances change. A leader leaning too heavily upon a past reputation (khaleesi! mhysa! breaker of chains!) and reluctant to take accountability for fresh missteps deserves our extreme suspicion. Authority and esteem must be continually renewed and continually earned from the people. It's a serious mistake to say that the formerly wheel-breaking, slave-liberating Daenerys is not now a villain by virtue of having done good deeds before.
III.
Power should not be an end in itself, informed by personal, self-serving agendas or biases.
At this point, Daenerys has spent considerable screentime speaking of "taking what is hers," of her birthright, and of her dragons (a proxy for herself as queen) eating "whatever they want." But do we know what her vision of the day-to-day act of governing is? Do we know what her plans for the ordinary people are, beyond vague and lofty exclamations of "liberation"?
Daenerys’s power is self-interested, a broken record of “I take the throne” whenever she is asked about procedures. Sansa’s “what about the North” falls upon unhearing ears. Daenerys is also personally insulted by Sansa's pragmatic, empathetic exhortations to allow soldiers to rest and heal, choosing instead to move ahead with a major military offensive. Worst of all, Daenerys justifies the burning of King’s Landing as a reasonable and necessary stepping stone to her personal, shapeless idea of a better world. I've seen personal “grief” (e.g., over Jorah and Missandei) suggested by Daenerys fans as a justification for her King’s Landing decision, but if anything, the influence of personal grief upon a decision like that is as damning as any other context would be.
Power that cannot separate the personal from the impersonal - and power that is self-interested, self-justifying, and offers no acknowledgment of those under its control - comes frighteningly close to being evil. And power so brittle and egotistical that it views dissenting opinion as a threat or insult…is evil.
IV.
Some internal uncertainty over choices and values is good.
It means we know the importance of weighing options and scrutinizing a decision, and we know the importance of looking to others for diversity of opinion. In other words, it means we have a vital sense of humility regarding the value and importance of our own limited perspectives and judgment.
Daenerys, however, is unwaveringly confident that she "knows what is good," opposite Tyrion and Jon's confessed uncertainty. She says her subjects "don't get to choose" because, as she's driven home over several seasons, she believes she has the inborn ability to know what is best for all.
A leader so rigidly and militantly convinced of their own perfect sense of direction is dangerous. A society is freer, safer, and better off with the freedom to deliberate with others and risk a poor choice under those circumstances, than to give over absolute control to a single, unquestioned authority. How can we count on such a person to be balanced and principled all of the time? What happens to the rest of us when they make a mistake? What happens when they can’t own up to a mistake or can’t see that they’ve made one?