Not according to the Dramatica definition.
the author's assessment of whether or not the Main Character has resolved his personal problem
The notion that the good guys win and the bad guys lose is not always true. In stories, as in life, we often see very bad
The audience may not like the ending or think that it was happy. But happy and good are not the same thing. And as far as Dramatica is concerned, if we're saying that Thanos is the Main Character, then the smile in the sunset at the end of the movie is the author showing that the Main Character has resolved his personal problem.
After all, if you were rooting for Thanos, then you would be happy with the outcome of the story.
On the other hand, if you're saying that one of the other characters is the Main Character, then sure, the Judgment could very well be Bad, and match up with the horrible feeling that the audience left the theater with. But for all intents and purposes, in this story, the Main Character got what he wanted and felt good about his choices overall. That's the Judgment of the story.
The problem with it does bring up is one of inconsistency in terms of theme. Whereas every other character who tries to "trade lives" for the greater good ended up failing and subsequently being punished for it in the story (i.e. Wanda and Star Lord). Thanos traded a life for the greater good, and ended up getting what he wanted and being able to enjoy a sunrise the next day. Of course, being that this isn't the end of Thanos' story, that sacrifice could come back to haunt him later on.
However, in this story, where everyone else suffered when they tried to trade a life for the greater good, Thanos did not. If he had, or if he felt bent out of shape about it for longer than it took to hop worlds and get into another fight, then that would be a different story. As it stands, when you weigh out the good with the bad for Thanos, it averages out on the side of good in terms of him being able to resolve his personal problem with the Universe.
Besides, the objective story points in Dramatica aren't about how the audience will feel about it. It's about what the author is trying to say. (Which is why I bring up the inconsistency in themes.)