Suffice to say, a lot of people were disappointed (or at least bewildered) with the development of Daenerys in the most recent episode of GoT.
Herein, a few thoughts about how it could have been done better. Note, there are obvious SPOILERS here. Yes, SPOILERS:
(1) I said before that if they wanted to make Dany a villain, there were better ways to do it than have her suddenly decide to engage in gratuitous mass murder. Here's one:
Daenerys' forces destroy the fleet and most of Cersei's army (just like in the actual episode), but Cersei manages to barricade herself in the Red Keep with a relatively small force (not enough to pose a serious offensive threat) and many thousands of trapped civilians. She refuses to surrender. Daenerys orders Drogon to burn down the Keep, killing Cersei, but also all the civilians. This alienates Tyrion, Jon Snow, and others, and sets up the final conflict. Its villainous, but a reasonable extension of her previously developed character (she is willing to be harsh when necessary to defeat her enemies, and this trait is augmented by anger over the deaths of Missandei and Raegal). Another advantage of this scenario is that it requires little or no change to the plot as developed to this point (although I dislike many of the decisions made in Seasons 7 and 8).
(2) Another superior strategy for making Dany a villain would be to further develop the issue of the North's demand for independence. Let's say Dany rejects this demand outright and offers little in the way of autonomy as compensation. She sees even a quasi-autonomous North as too great a potential threat to her power and as a rejection of her right to rule (which we know she is deeply committed to). The resulting conflict (which, perhaps, takes place after Cersei is dispatched) pits Daenerys against sympathetic characters (Sansa and others), and results in extensive carnage for no defensible purpose on her side. This would require some alterations to the plotline where Dany grants independence to the Iron Islands and even says others are entitled to ask for independence (in season 6). But the hole can easily be filled by having her point out that the Islands are not a fully integral part of Westeros and certainly far less significant to the monarchy than the North. She's willing to give up the former, but not the latter.
(3) A good writer or producer can undoubtedly think of other possibilities, perhaps better than the above. But Option 1 is obvious enough (and easy enough to do) that Benioff and Weiss deserve severe criticism for not pursuing something like it.
(4) I personally still would have preferred a resolution where Dany turns out to be a reasonably decent ruler (or at least better than the alternatives), but still not worthy of wielding the power of the Iron Throne (because no one really is). That could have driven home the point (implicit in the books and earlier seasons of the show) that the problem is institutional, not simply a matter of the personalities of individual monarchs and lords. That, however, would have required a significant restructuring of Seasons 7 and 8 (which might be a feature, rather than a bug, given all the problems with the plot of those seasons). If this approach butterflies away idiocies like the wight expedition, so much the better!
(5) But I understand that the story has to reach the conclusion that George RR Martin wanted (in conjunction with Benioff and Weiss), not the one I want. Given that constraint, something like 1 or 2 above is an obviously superior strategy.