Suppose that The Godfather: Part III (1990) is considered appalling, but you can't put your finger on exactly why, mainly because there are a plethora of reasons, most of which you lack the training/education/expertise to comment in-depth on (e.g. the writing, directing, editing etc.), so you use what you consider to be a disastrous moment/scene as an example, and think "this pretty much sums it up", for example this scene, what would you call a scene like that? A single word or expression is satisfactory.
As an example:
"The Godfather 3 is so bad, for so many reasons, but here is a ______ that perfectly represents everything wrong with the movie."
An expression is also acceptable, and the example I gave is flexible (doesn't have to be structured as it is in the example).