The central conflict in Judy Blume's Blubber is actually a bit unusual because Jill, the protagonist, doesn't behave like a protagonist at all; she is instead much more of an antihero. A protagonist is the main character in a story who grows and changes as a result of overcoming the conflict; an antihero is a protagonist who doesn't have the typical characteristics of a protagonist, characteristics that make the reader love the protagonist such as "bravery, strength, charm, ingenuity, etc." ("Anti-hero," Literary Devices). Instead, Jill, the antihero, is a cruel bully and part of the in-crowd led by Wendy. When Wendy begins bullying obese Linda, Jill and the rest of the class follow suit. However, Jill does occasionally get into trouble for her actions though she never agrees to having been wrong. Since Jill gets into trouble but disagrees with the rest of society's view of right and wrong, we can call Jill's conflict a character vs. society conflict.
One example of Jill getting into trouble is seen when she and her friend Tracy are made to rake Mr. Machinist's yard for eight hours for having egged his mailbox. In their view, Mr. Machinist is just a grouchy old man, and "nothing is too mean for Mr. Machinist ... . He deserves it" (p. 40). However, Jill's father opposes Jill's belief about just deserts by arguing, "[I]t's not up to you to decide who deserves what in this world" (p. 99). Despite her father's wise words, Jill never accepts that she was wrong.
The story reaches its climax when Jill takes bullying Linda to the extent that Linda is imprisoned in a closet, waiting to stand trial. Wendy presides as judge, and when Jill thinks Wendy is taking the idea of the trial too far, she double-crosses Wendy by letting Linda out of the closet. Wendy vows revenge. The next day at school, Jill and Linda have changed social places. Linda is now part of the in-crowd, and Jill is the one who is mercilessly bullied. But, still, Jill never repents her actions. The story somewhat resolves when Jill learns how to cope with the bullying by bullying the bullies right back and by befriending quite Rochelle. However, the ending of the story also makes it quite clear that Jill never learned how to be a more compassionate, gentle person; therefore, she remains in conflict with society by always thinking she is right, and the story never fully resolves.