What is the significance of Tessie's final scream, "It isn't fair, it isn't right"? What aspect of the lottery does she explicitly challenge; what aspect goes unquestioned?
With the words "it isn't fair, it isn't right" Tessie is explicitly challenging the fact that a practice, one of which she had been a part of for quite some time, has finally caught up with her. Now, she will meet her end the way others did when Tessie participated actively in the process of the lottery.
Aside from her own demise at the hands of the very people that she once helped to end the lives of others, she is also questioning the establishment: That powerful minority that, for decades, has managed to manipulate an entire village into preserving anachronistic traditions. The Lottery is both barbaric and useless. This juxtaposition of descriptors demonstrates the futile mindset of these villagers, who have allowed this practice eat away at their already necrotic common sense.
Yet, there is a lot that still goes unquestioned.
It is arguable whether Tessie's anger is not necessarily directed at the tradition of the lottery, itself. It is clear that, from the beginning, she had been anxious about what day it was, and she even showed up late for the drawing of the names.
There is no evidence that she had ever gone against the system, nor that she had done anything previous to this day that would prove that she is a renegade fighting against "the injustice of it all". It is simply "not fair" that it was her name that was drawn and not someone else. Yes, she was angry at the system and at the establishment, but mainly because she has had to undergo the lottery as the elected victim.
Still, Tessie does not question why the lottery still goes on. In fact, she obligingly attends the meeting as expected, although she is late. She does not question (or has never questioned) how come innocent people have to die. Nothing was never questioned on why the lottery still goes on and, except for bits and pieces of information spoken by some of the town's elders, all that we know is that the lottery was celebrated for generations as a way to get good crops, and that it has changed throughout time without ever being questioned. "There has always been a lottery" is the perennial message of the story. As long as nobody questions it, it will forever remain active.
Another aspect of this story that often goes unnoticed is that even before Tessie questions her own demise, after her family is chosen, she questions the rules that allow her married daughter to be considered as part of the daughter's husband's family unit. Her questioning at that point is so self-serving that she is willing to put her own child at risk. If her daughter were to be considered as part of her family unit, this would make Tessie's odds of not being chosen much better. She is completely willing to put her daughter's life on the line to save herself, or at least to better the odds. This has always struck me as one of the more odious aspects of Tessie, and it has occurred to me that Jackson deliberately made her a monster, so that the reader would feel some grim satisfaction in her being the sacrifice.