In my mind, the strongest case can be made for violence as the primary theme in Jackson's "The Lottery." The entire ritual in the story is predicated upon socially sanctioned violence. The attitude of the townspeople to what they perceive as must be done in the name of tradition is a reflection of how violence has become accepted with banality. The veneer of peace and civility is maintained because of violence. Someone in the town must be the recipient of cruelty and violence. Tessie's protests against violence are poignant, as evident in the final words "It isn't fair! It isn't right." Yet, at the same time, they are motivated by her selection and would presumably be absent had someone else's name been pulled. Mrs. Delacroix, by all accounts Tessie's best friend, abandons her in the name of violence when she finds the largest rock to use against her.
Jackson's story is rooted in how societies that embrace violence cannot be called civilized in any form. The story delves into the thematic application of how violence is a part of human identity and social organization. Jackson wishes to bring out this aspect of the story as something that the readers would be willing to question in their own world. It is for this reason that violence becomes the primary theme of the story.
One of the biggest themes in The Lottery is the unpredictability of mob behavior. As soon as someone draws a wrong slip of paper, the entire town steps up against them to eradicate them. They stop being a person and a member of the town as soon as they draw the slip, regardless if they have been there their whole life or not.
Another big theme is tradition. The Lottery has become a tradition in the village for many, many years, and the most people accept it without question. In the story, it says "The people had done it so many times... they only half listened to the directions". This statement is a great supporter of the theme.
Hope this helps!