"The Lottery" doesn't have a direct protagonist, as the story is more of a vignette, and most of the characters are given equal time. In the sense of a more sympathetic character, Tessie Hutchinson is the only one who is singled out, even though more for the purposes of the twist ending than anything else.
Suddenly, Tessie Hutchinson shouted to Mr. Summers, "You didn't give him time enough to take any paper he wanted. I saw you. It wasn't fair!"
(Jackson, "The Lottery," classicshorts.com)
Because of this, she has very little character description; the most that can be said is that the sudden realization of being picked in the lottery changes her opinion of the fairness of the ritual. As the story starts, she arrives late, laughing that she forgot the day; by the end, she is screaming of the unfairness of the Lottery. Changing her mind, as the other characters seem unable or unwilling to do, shows that she would be able to grow as a character in a longer story; sadly, her fate is the twist on which the entire story hangs.